Er, realistically, both have 512 MB of RAM, I don't understand why you think the PS3's setup is better.
The 360 has the better GPU, the PS3 has the better CPU but its harder to write apps that actually utilize it and poorly optimized apps will run worse.
Cell does not automatically floor a triple core PowerPC; an unoptimized app will only use the single PowerPC core in the Cell, and optimized apps are really hard to write.
Without having to run an OS, with very optimized memory handling? 512 MB is plenty. Windows Vista takes up like 512 MB of RAM while idling.
The PS3 has a few major flaws thanks to using the Cell, where developers have to bypass something (can't remember what it is, but it's slow).