PS3 -is- much better...
...if you believe the hype.
However, Sony themselves have quoted performance of 1.8 terraflops (theoretical) and the 360 has a -theoretical- performance of "over a Teraflop" so my guess is the performance comparisons between the two will be much the same as this or any other console generation, and once again, it will come down to the individual's own brand preference.
I'll be getting a 360 mainly because I have an Xbox and want to continue with many of the exclusive titles I enjoyed, like Halo and Morrowind.
Later, I'll probably get a PS3 for and/or Revolution, depends on price at the time and the quality of titles that catch my eye.
Pfft, Just like this (and every other) generation really...