Dan Pouliot has assembled a thorough (but unscientific) comparison of Mac OS X Jaguar and Windows XP. I don't want to spoil it for you but OS X wins despite wrongly losing to XP on security, video editing transitions and titles, and remote control (SSH is more secure and nearly as useful and Remote Desktop).
I particularly like the coverage of dialog boxes. It's one of the things you can almost overlook while using OS X until you switch back to Windows and realize how crappy Yes/No/Cancel is.
Read all the details at xvsxp.com