PS3
I've owned both so here goes...
Bluray won. Load times on PS3 seem faster. More bang for your buck (last time I checked PS3 prices were better than Xbox 360). Better built machine and harware. Some peeps say graphics are better; maybe they are maybe they aren't, I can't really tell. Free online. Etc.
People say 360 has more games, but how many games are you going to buy anyways? The BEST games are almost all cross platform (COD4, Skate, GTA, etc). Even with exclusives, I think you'll find PS3 has a very solid line up. Online for PS3 is also pretty decent and it's FREE.
My number one reason to go PS3 would be durability. Within a month of getting my 360 it broke down. I got the infamous ''Red Ring of Death''. The Xbox is just a straight up badly built machine.
Still, I would get a Wii if I were you.