Your PC friends are mostly correct. Macs had a huge graphics/color/fonts lead in the 80s, but Windows largely closed the gap since then. Most cross-platform graphics apps are the same in Mac or Windows, meaning the remaining differences are down to how the OS handles things. If you are one of the many Windows users who can't stand Vista, that's the deal-breaker...get a Mac.

I like Macs because they have no problem handling lots of memory-hungry apps during a long work day. One week later and it can still be running without having to reboot the OS. I've been surprised at what I can throw at OS X on my laptop and the system keeps humming along. Now, if you're a PC technician type who gets into babysitting the OS all day long, PCs are as good as Macs. But, if you just want to get real work done, Mac OS X is very low maintenance, meaning you can just do what you need to do and never think about the next time you need to defrag or reimage the system.

As far as cross-OS compatibility testing, when I have to I start up Windows in virtualization within OS X through Parallels Desktop. I almost don't use my ThinkPad anymore.