Simple truth?
It doesn't really matter.
The main differences are: the controller, how online works, a limited number of exclusives per console, and that the PS3 plays blu-ray.
If you care about blu-ray, your decision may be a little easier. It obviously affects movies, but also when games go multi-disc on the 360 because they don't fit on a normal DVD - whereas they'll fit on a single blu-ray. If you don't care about that, then it's a toss-up based on other factors.
Personally, I prefer the 360. It tends to be the lead console platform more often than not, especially for games that have life on the PC-side, so cross-platform games - that is, the majority of games made - run better on the 360. Also prefer the controller, even though I was a PS1 and PS2 owner.
Truly, though, neither one is a bad choice. Just find out about some games you want to play, buy those games and whatever system they're on.