You should buy a computer based upon how you're going to use it most importantly. Considering that PCs cost about half of over-priced Macs.... Suggest you go to Mac only if (a) a PC won't do the job for you (AND you have some notion that the Mac WILL), or (2) you just wanna Mac for status. (Wifey argues for a Mac because "everybody else at the University has one"... Pish-posh. I'd rather run a PC and spend the price diff on burritos and beer... but I'm probably not cool enough to deserve a Mac.)
True words Just make sure your screens are not hit by direct sunlight due to glare. FYI glossy screens are polarized filters. helps
For laptops, IMHO Mac beats in every respect. I would be very reluctant to buy a Mac desk top other than my semi-girlfriend (I told her to expect minimal love from me) or, uh, secretary. Or maybe future 3 year old. With the laptops, the hardware by itself is far superior to the other plastic stuff out there. also the warranties are unrivaled. The macs effectively come with an insurance plan. very generous from my experience. Anyways, yes, I run Win7 on my MBP 17" side by side with Lion without any problems. I can copy/paste between the two, drag and drop files, listen to sound on Windows, run the processor 100% in Windows, watch movies on Windows..... works like anything else on the computer. Definitely wasn't what I was expecting when I first used it. I would recommend VMWare because Bootcamp requires a reboot. Edit: OSX Lion is a superior OS for laptops than Win7. I heavily favor windows in desktops still. Lion makes mail, web, etc. very easy, and the trackpad functions makes it the closest thing to a multimonitor desktop as possible.
You'll definitely need vmware for pc apps. Some stuff, like TWS to Excel DDE, just doesn't work at all on the Mac version of Excel.
I just don't think i'd be comfortable trading on a Mac. 90% of trading apps are PC native - why try to mix platforms when you could have a PC for trading and a mac for everything else?