With all the news being about that other system, there is a great article up at PS3Blog.net about why you should wait for the PS3.
The big two for me are on the list:
Cell processor. The Cell processor looks to eclipse anything that’s come before. The physics power of the 7 SPE’s will make for games that rock!
Blu-ray. The PS3 support Blu-ray drives for higher storage and for movies in HD.