You might want to think about your needs for technical computing. Are you doing any Econometric type stuff with your computer, i.e. Monte Carlo Simulations, time series analysis etc... If so... PC wins.
If you are just doing word, ppt or spreadsheets then Macs are great. I use PC laptops and desktops at work and have a Macbook Pro (with dual boot to Windows) for myself. If I can, I use my Mac as it is much more stable and faster than when it is running as a PC. Its particularly good at Excel. But I have Snow Leopard and when I had Leopard installed Excel on Mac was completely useless for any real data sets. So if you hear someone say Macs aren't good at office tell them to get Snow Leopard.
But there is a downside to Office on Mac. Mac office doesn't support VBA which can be a pain in the arse if you need to write Macros. i can get by without it but it is annoying. This might change with Microsoft's .NET platform but at the moment doing anything technical in Office on a Mac is a pain but they're great at basic spreadsheets and such.
I use a lot of specialist software that is only available on PC so I have a dual boot function. The downside is that my Mac blazes through its battery on Windows but I can run it all day without a charge when its running OS X.
One of the great things about Macs is their build quality, its unsurpassed. IBMs seem pretty much the most solid PCs around but they're still not Macs. The stiffness of the keyboards support is so nice if your typing all day. The screen are also incredible. My work laptop is a Dell XPS 16, supposedly one of their top of the line laptops. The keyboard flexes, the chassis flexes, the fan is constantly on, its constantly hot etc...all annoying and all not a problem with the Mac. But you definitely pay a price for this. But then again you'll pay a premium for a really well built PC like a Lenovo or Sony too.
If you can stretch to it then I'd get a Mac and install windows and office too in case. IN the Uk there is a deal on where you can get Windows 7 and Office Ultimate (has everything) for thirty nine pounds 9around $45)! And its legit, its direct from Microsoft. I know they do this in the US too but only at certain times of the year so it shouldn't be expensive (everything in the UK is more expensive than the US). All you need is a University email address. Here's the UK website:
http://www.microsoft.com/student/discounts/theultimatesteal-uk/default.aspx
I'm guessing if you go here you'll be redirected to the US equivalent