Got a 360, play my room-mates PS3 >2 a week.
Hardware
The PS3 is built solid. The old xbox 360s are build a bit shitty - even if you don't get red rings you wont feel like it's a high quality product.
The new xbox 360s (?slim) may change this - they certainly look better made.
The graphics are pretty much the same as far as I care -
gamespot used to do comparisons.
Games
A lot of games are available for both systems. Xbox you're getting Halo which is a deal breaker
for me. PS3 had never made me regret my choice with a game title.
Extras
Your online experience is going to be better on the 360 but you're going to pay for it (I'd rate it higher than PC online experience - not including MMOs).
PS3 is a top quality bluray player if you're a movie buff. However, there is netflicks etc in HD for the 360.
Conclusion
I've not regretted getting my 360, red rings and all.