* Jun... what is your main use for XP or Vista ?

is it going to be games? (if that's what you want better stick to BootCamp - or anything that does any heavy 3d rendering). If it's everything else, Parallels is right for you. I believe Parallels has a demo you can try, why not check it out. I'm using both Parallels and Bootcamp and have different uses for each. But most of the time I'm on Parallels.