"Should I upgrade the Mac I have or buy a new one?" It's a question that faces every one of us at some point, and it's not always easy to answer. In a lot of cases, owning a Mac can complicate this answer simply because the darned things are so long-lived. It's a lot easier to justify replacing some $500 Dell econobox after a few years, since it's probably got one foot in the grave by that point anyway, but I've known people who happily trundle along on Mac hardware that's nearly a decade old. In fact, I used to be one of those people; my first Mac was a 1998 PowerBook G3 that I bought used in 2004 and used until 2007.
I'm facing that "upgrade or buy new" question myself right now. Installing OS X Lion on my Early 2008 MacBook Pro has made it clear my hardware isn't humming along the way it used to. I've got a choice between throwing in another 2 GB of RAM and replacing my dog slow HDD with a much zippier SSD, or just ditching my current Mac altogether and replacing it with a current MacBook Air.
Several factors are complicating my decision to upgrade or replace my current Mac, and these are pretty common questions that every Mac owner is going to have to answer for themselves eventually. I've worked out a decision path below that should help guide you in your choice. Note that this is only a recommendation; if you're perfectly happy chugging along on that OS X Tiger-running PowerBook G4 from 2004, don't let me stop you. But if you're like me and finding that your older hardware is getting in the way of your workflow, it's probably time to start asking the hard questions.
I've broken things down in stages, based on the age of the Mac you have now.
0-2 years old: Consider upgrading your current hardware
Any Mac this young is fully capable of running OS X Lion, and there's nothing stopping you from syncing it with the latest iOS devices other than keeping iTunes up to date. If your Mac is still covered under AppleCare, still runs all the applications you need to run, and isn't showing any signs of decrepitude, there's probably no real reason to buy a new one at this point.
If you're finding your Mac is running a bit slower than you'd like, the best thing you can do for it is to throw more RAM in there. While OS X Lion's minimum RAM requirement is only 2 GB, I've found it suffers tremendous performance bottlenecks with that little RAM. Even the 4 GB I have in my Mac often doesn't feel like it's enough, especially since Safari seems to leak memory like a sieve. If your Mac can handle 8 GB of RAM, and you can handle laying out the money for it, then go for it.
Contrary to popular belief, upgrading your Mac's RAM by yourself does not void your AppleCare warranty. Apple even includes instructions on how to self-upgrade the RAM in the instruction book that comes with your Mac, and they're also on Apple's support site. In most cases the only tool you'll need is a screwdriver. RAM upgrades are not complicated in the slightest, and if you're even moderately competent with tools, there's no reason to pay someone else to do it for you.
The next best thing you can do for your Mac is upgrade its hard drive, though this is a more complicated procedure and one that's probably not going to be as easy to pull off on an iMac or Mac mini (if you can even do it at all). If your Mac came with a slower 4200 or 5400 RPM hard drive, like mine did, you may find that to be a huge performance bottleneck once your physical RAM fills up and OS X starts using your hard drive to supplement it with virtual memory.
If the problem facing your hard drive is that it's running out of space, unless you have a Mac Pro (which makes swapping in a new drive trivial) I'd recommend buying an external drive instead of replacing the internal drive, especially if you have a MacBook or MacBook Pro. You can buy a hard disk with higher storage and replace it yourself on those models, but considering the price you'll pay for a laptop-class hard drive versus an external drive of the same or higher capacity, it's probably not worth it unless you vitally need a terabyte of data to follow you around everywhere.
If you're like me and finding a traditional platter-based hard drive is too slow, swapping out your internal hard drive with a solid state drive (SSD) is a great way to see immediate and often startling improvements in data access speed on your system. The drives come with two obvious tradeoffs, however. First, they're extremely expensive, especially compared to a traditional hard drive; you can expect to pay US$400 or more for a decent 250 GB SSD. Second, these drives generally don't come in larger sizes unless you're willing to pay a huge premium.
I find that I can get by just fine with 250 GB of storage on my internal drive, with the majority of my media housed on much larger external drives. That's why I'm considering replacing my current MacBook Pro's drive with a 256 GB SSD if I can't find a way financially to upgrade to the new MacBook Air instead, which also has an SSD in the same capacity.
2-4 years old: It's a tossup
If your Mac is between two to four years old, the "upgrade or replace" question gets more complicated. A two-year old Mac should still be plenty fast and capable of running nearly all modern software without feeling bogged down, but the four- to five-year threshold is typically when Apple begins phasing out software support for older Macs. Putting more money into your current machine via upgrades makes more sense toward the beginning of this cycle, but toward the end of it you may find the money is better spent on getting a new Mac instead.
Resale value on Macs is typically higher than that on PCs, but the market value for your Mac does start to drop precipitously after the second year. If you're like me and you can't afford to buy a new Mac unless you can sell the old one first, it might be a good idea to consider selling your current Mac around the two-year mark, especially if you purchased additional AppleCare coverage. Having an additional year of warranty coverage available to potential buyers will be a huge point in your favor should you choose to sell your Mac.
If you can get fair market value for your machine (after 2 years, typically 40-50 percent of what you initially paid for it, depending on the model and its condition), selling your current Mac every two years may mean you'll wind up paying full price for a new Mac only once every four years or so. A lot of the savvier Mac owners out there go through this biennial selloff, and if you can afford to outlay around 50 percent of the cost of a brand-new Mac every two to three years, this is definitely the route I'd recommend most if you're interested in keeping your hardware up to spec with Apple's latest software.
After your Mac is over three years old and has no AppleCare coverage, getting a decent resale price becomes much harder. And, given my personal experience with Apple's notebooks, I don't recommend running around with an out-of-warranty MacBook for any longer than you have to. Once the warranty coverage expired on my current Mac, the only thing that's held me back from replacing it with a new one is the fact that I can't afford to.
In my case, I'm kind of stuck because I waited too long to sell my current Mac, which is now 3.5 years old. I've tried to sell off my Mac already, but thus far I haven't received any offers that even come close to the fair market value for it. Since I can't afford a new Mac, but my current Mac's performance no longer meets my needs, I basically have to upgrade my existing hardware if no one makes me a fair offer for it first. Learn from my example: if you even suspect that your Mac is going to be too slow for your needs after three years, consider selling it off well before it gets to that point.
4 years+: Buy a new Mac
I recently had a reader ask if it was worth upgrading his iBook G4 to Leopard so he could update iTunes and sync his ancient Mac with a newly purchased iPad 2. I said no, for several reasons. First, his machine is over six years old, and as a PowerPC machine, its maximum possible OS version is now two major revisions behind. Throwing more money at that machine makes even less sense when you consider that the iPad 2's benchmarking scores are almost exactly the same as the iBook he'd be syncing it with!
If your Mac is more than four years old, and you're finding it too slow for your needs, it's about time to buy a new one. Sure, you can buy more RAM or a faster drive for it, but should you? The only way I'd give a "yes" to that answer is if you simply flat-out cannot afford to get a new machine. At four years old, your Mac will be over a year out of warranty, facing an increasingly dismal resale value and quickly approaching the end of its useful life as far as its ability to keep up with the latest software.
What do I mean by that? OS X Lion runs on most Intel Macs, but not all. Many of the first-generation Intel Macs released in 2006 run on 32-bit architecture, and that's hardware which Lion no longer supports. Those earliest iMacs, Mac minis, MacBooks, and MacBook Pros are therefore stuck running Snow Leopard or earlier. That means those Macs have at most four or five years of remaining software support from Apple (i.e., security updates, iTunes support, and so forth) before they're considered obsolete and no longer supported at all.
Released in 2009, OS X Snow Leopard was the first Intel-only version of OS X, meaning all Macs released before 2006 are only capable of running OS X Leopard or earlier. These older PowerPC-based Macs can likely expect to see support for even the most basic things such as iTunes updates vanish entirely sometime within the next few years.
In 2007, Mac OS X Leopard dropped support for all PowerPC G3 Macs and all Macs with a G4 processor running slower than 867 MHz. That means with the exception of some of the more powerful Power Macs and PowerBook G4 models, virtually all Macs from 2002 or earlier (and even a few of the 2003 Macs) are incapable of running Leopard.
If that trip down OS X Memory Lane shows anything, it's that once your Mac passes its fourth year, its days are numbered as far as Apple's concerned. I won't be surprised at all if the next major revision of OS X comes out in 2013 or 2014 and drops support for all pre-unibody models of the MacBook lineup. The inability to run the most current version of OS X on your hardware doesn't automatically mean your Mac is useless, but it does make things much more complicated for you than they need to be.
The reader discussed earlier is just one example. Using a Mac released over six years ago, and still running an OS released in 2005, he found himself unable to sync his iBook with a new iPad 2 -- a machine that actually matches or outclasses his old Mac's performance in nearly every way. He can spend $130 or more to upgrade his obsolete Mac to Leopard and gain the ability to sync it with his new iPad, but is that $130 a wise purchase for a Mac whose maximum performance is substantially inferior to even the cheapest Macs available today? No way.
If you find yourself at the point where your current hardware is no longer meeting your needs, the decision to upgrade or replace it is going to depend on your financial means and the age of your Mac. If I had my way, I'd buy a new MacBook Air today and send my current MacBook Pro to a nice country farm where it could frolic with the other old Macs in the sun all day long ... but since it looks like I waited too long to sell my Mac and get what I consider a fair price for it, I'm instead stuck spending money on upgrades to keep it chugging along for another year or two until I can afford to replace it. If you're at the two- to three-year point in your Mac ownership and finding it too slow for your typical usage, don't hesitate -- put that thing up for auction and start shopping for a new one, because it'll actually save you a lot of money in the long run.