I've looked all over for this comparison but can't find it . . . how much difference, really, is there between these two machines? iMac 3.06GHz 4GB RAM 500GB @ 7200 ($1149) MBP 2.26GHz 4GB RAM (I'll upgrade the RAM myself) 160GB @5400 ($1099) I don't need the storage space of the 500GB, but I'd like the fastest machine in this price range. Making it a laptop would be nice, but I'm not convinced it's necessary. In other words, how much difference is there between 3.06 and 2.26 GHz, and does the slower HD really make much difference? Thanks.