You could call 15.6-inch screens the sweet spot for most gaming notebooks. They're large enough to give you a nice view of the action but small enough to make laptops portable. But, just as with any PC, you have a few options. If you prefer a smaller screen, you can take a look at 13- and 14-inch options, like the Alienware 13 and last year's Razer Blade 14. Just pay close attention to how much they weigh: The Alienware 13 currently clocks in at 5.8 pounds, heavier than most 15-inch laptops we've seen this year. And if you want to go all out, take a look at 17-inch notebooks. They're tougher to travel with, but far more immersive once you start gaming and can pack in more powerful hardware.
Choosing the right screen resolution and refresh rate is also important, since that's directly tied to your gaming performance. At this point, you'll want a 1080p screen. That might seem a bit regressive in the 4K era, but it'll let you reach higher frame rates. 1080p is also a compelling option with 120Hz- or 144Hz-refresh-rate panels, like we've seen on plenty of gaming notebooks this year. That higher rate smooths out gameplay as you move beyond 60 frames per second. Typically, that would lead to stuttering and other performance issues on a 60Hz screen.
The standard solution for dealing with high-frame-rate issues is Vsync, which caps gameplay at your monitor's refresh rate. But that introduces some problems of its own, like stuttering and slowdowns. That's where variable-refresh-rate technology like NVIDIA's G-Sync and AMD's FreeSync comes in. They match how your screen is refreshing with your gaming performance. That's useful for high-fps games, as well as for demanding titles where you might not reach your monitor's maximum refresh rate. And most important, it avoids the problems you'd typically have with Vsync.
G-Sync screens are expensive, though, and we haven't seen the technology implemented in many of the 120Hz and 144Hz displays in the recent wave of gaming laptops. Similarly, there aren't many FreeSync-capable laptops around, since AMD's mobile GPU still hasn't arrived. At this point, you're better off prioritizing screens with higher refresh rates.
Moving beyond 1080p, you'll also find 1440p (2,560 x 1,440 pixels) on some laptops. That offers a slight improvement in sharpness, but it'll be more noticeable when you're browsing the web or editing documents than it will be while playing games. And of course, 4K displays are making a big splash this year. You'll pay a huge premium for those, though, and we don't recommend 4K unless you really need those extra pixels.
If your machine doesn't have NVIDIA's GTX 1080, you'll have a hard time reaching 30fps, the bare minimum for decent gameplay, while running many titles natively in 4K. That means you'll likely end up running games at a lower resolution, which defeats the point of getting a high-res display in the first place. Using LCD screens outside of their native resolution also leads to blurriness and other image-quality issues. If you plan to binge a lot of 4K video while your eyes are inches away from your screen, then it might be worth it, but for most folks it won't be. Instead, put the money you'd spend toward the 4K upgrade on a decent gaming monitor or a 4K HDR TV.
Other points to consider
Get at least 16GB of RAM. That gives you room for plenty of multi-tasking, especially if you want to stream gameplay.
Storage is important! It's not unusual for large games to go beyond 40GB these days. Get a 256GB SSD at least, and if there's room, snag a secondary drive just for games. If you're looking at a machine with an M.2 SSD, check to see if it's removable for upgrading in the future. Some laptops also offer spare M.2 slots for adding a secondary SSD.
As with any major tech purchase, try to get your hands on a few gaming laptops to figure out what you really want. It's hard to get a sense of keyboards, displays and weight just by reading about them.
OLED and HDR are slowly showing up in gaming laptops, but they're limited to a few models, like Alienware's R13, and they're very expensive.
Don't forget your accessories! You'll want a good gaming mouse and a solid pair of headphones.
So what should I get?
If your priority is smooth gameplay, I'd recommend a laptop with a 15.6-inch 1080p screen and either NVIDIA's GTX 1060 or 1070 Max-Q GPU. The former will run most games well at 60fps and beyond, while the 1070 will let you reach even higher frame rates and better-quality graphics settings. Mid-range machines like HP's Omen and some of Dell's Alienware models are a good start. If you've got a slightly bigger budget, you should consider laptops with high-refresh-rate screens: MSI's GS65 Stealth Thin, Gigabyte's Aero 15X, Razer's Blade and pricier Alienware configuration.
But if you're on a budget, stick to machines with the GTX 1050, 1050Ti or 1060 Max-Q, like Dell's G3 and G5 series. You won't get high-refresh-rate monitors with these, but they'll have enough horsepower to reach a silky 60fps. They're ideal if you're mainly playing MOBA titles and undemanding games like Overwatch.
It's easy to get overwhelmed by the number of options today, but that variety is ultimately a good thing. What was once a category filled with huge, ugly monstrosities now includes genuinely gorgeous machines that aren't much heavier than a MacBook Pro.