Having never owned a mac before, but in need of a laptop, i'm 100% sure i'm getting a mac tiger OS just seems so much better than XP. between the 12" and 15" powerbook, the main difference is just screen size right? is the minute processing difference noticable? keep in mind i am used to my pc P4 2.8 HT 1gig 2X10,000rpm SATA RAID 0 am i gonna be wanting more speed? i know the macs process differently and it makes them seem as fast or something like that. But i dont know the specifics. Can someone enlighten me?