The 360, and here's why:
While it is true that the PS3 has different and more capable hardware, most people won't program for the cell processor fully and those that do haven't really shown much favorable progress. You can mention games like Resistance, Killzone, God of War, and Uncharted, but save for the appearance (I can't comment on God of War) the plot of those games is low, the balance and difficulty and gameplay construction is low and unfortunately, while I own a PS3 and play these games myself, the best games are found on the 360, and if ports exist on the PS3, you can still see that they are definitely ports and even when remastered they just aren't all that worth it.
As for the 360, it has the best online service for a once a year cost, is much easier and faster to navigate, has the best selection of "hard-core" and "action" and "story" games coming out, and even has the RPG department locked down due to their actions. Any game the 360 gets MIGHT be ported to PS3, but it's not better.