what software are you going to need to run? is that software all available on both the MAC and Windows? Is the software the same on both OSs? for example office is available for the MAC but its not exactly the same as the windows versions.
So, assuming all of the software will run on but operating systems what else are you looking to do with this machine? How long you looking to keep the machine? are you going to hand it down to some one else when you upgrade to a newer machine or sell it?
i find that i get the best resell value on my MACs and they seem to last (at least for me) than my PCs have in the past.
i would wait on buying either a MAC or a PC until after the release of windows 8. you will see a lot of changes to the machines that come with windows 8 so they are better optimized to support the new OS with this like touch screen and more sensitive track pad. Also i think we will the current windows 7 machines reduced in price to help get rid of the stock of "older" machines. Once they are out and you can go and play with them in a retail store go to a place like best buy that will have PCs and MACs where you can compare them side by side.
now if money is not an option and the software runs on both OS i would lean towards a MAC. i love the look and feel of the hardware. i think for the most part they are better built and there is a better integration between the hardware and the software. I also like the fact that apple stores are all over the place and its easy to walk in with the device and get support for it locally.
I am taking a few engineering courses right now and would highly recommend going with a Windows laptop. The Macs seem to do ok on the engineering side, but there is still more support present for software on the Windows side. Either one will probably be perfectly capable of accomplishing what you need them to do, but your life will probably be easier with Windows, the support structure is still so much better for most of the software out there. Windows 7 is a very easy to use OS so you shouldn't run into much of an issue there either.