Well, 2 or 3 years ahead anyway.
First of all the PS3 is going to be ahead because it was released more recently.
Also I , if I am not mistaken, the PS3 has hardware designed to go into a console game system while the XBOX is basically a PC in a console container.
Biggest factors working against the PS3 is probably the cost and the number of games available for it compared to the other consoles. Beyond that it doesn't have any downside that I can see.
Not in the GPU/Memory department. They skimped their because the Cell processor was expensive to produce. They actually use a worse and inferior architecture.
Also the Cell processor was not developed for gaming. Sony developed the CPU to be used an entire line of their products. The Sony gaming unit was pressured to use the Cell in the PS3 to help legitimize it's development.
There is a reason that most of the same games for the 360 look the same and in many cases look better on the 360 or run better (a la Madden).