You've already wasted your time posting this question in this forum. In the time it took you to collect and read the answers, you could have installed Windows on that machine and seen for yourself whether it was worth it. ;-)
Right in this very moment, I'm using my Vista 64 Boot Camp installation on my Mac, but sometimes I also don't know why I have it.
Then, when I look at it from my job perspective, I'm asking myself why I have a Mac.
The world where I make my money consists of Windows Servers and a few Unix(-like) boxes that do -not- have an Apple on them and that do -not- run OS X. Apple simply is a no-show in -my- professional world.
I've got to know a whole new platform in the few years since I'm using Macs in my private life, but it had little to almost zero impact on my career and professional life. Maybe it even was a waste of time and money to go down the Mac route in the first place: The world uses Windows, and I also don't feel special anymore when I use a computer (read: a Mac running OS X) that's most of the time not really compatible with the rest of the world. It's more annoying than it is fun.
Or to put it that way: You have a luxury problem and probably no real need for either machine, otherwise you wouldn't be thinking about what software to run on what machine. Both platforms are sufficient for casual web surfing, but only one is good for playing games and in almost all cases only one is good for professional/business needs.
I've yet to meet somebody who can truly exclusively and every day use ONLY OS X and software for OS X. Sooner or later, everybody either boots into Windows or fires up a VM with Windows. That says a lot about the position of Windows in this world and it also says a lot about the shortcomings of the Apple platform.
