I play on both, although I spend far more time on the PC than the 360. The 360 has its place. I play some games with my wife on it (Just got her into Soul Calibur IV). Some games work well on it, like racing games, platformers, sports, etc. I'm also looking forward to the Netflix integration and community games features in the new update.
But I love my FPS and RTS games, which just flat out suck on consoles. Hell, they're hard enough to get right on the PC. Why make things even more difficult? RPGs are very hit and miss. I prefer western style RPGs and they tend to get dumbed down on consoles and the interface is usually annoying. Mass Effect and Oblivion both suffered from bad design decisions due to being created for consoles. They're oversimplified and rather shallow. At least Oblivion got fixed by mods on the PC.
"The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts." -- Bertrand Russell (I think...)