Having owned both consoles I prefer PS3 (my 360 RLOD 3 times).
As someone mentioned in a previous post you need to figure out what type of games you prefer to play, if it's First Person Shooters like the Call of Duty series than you may want to get a 360. Reason I say this is because most FPS games are designed for the 360 and are just simply ported over to the other consoles or in the Wii's case stripped down.
Believe it or not (and I'm sure someone out there will be happy to correct me here) the PS3 is a more powerful machine, exclusive games such as God of War III and the Uncharted series look much better than some of the exclusives on the 360 due to the guts of the PS3, you can google it to see the differences.
I also saw someone post up "who cares about Blu-Ray" I want to add that not only is Blu-Ray far superior over the other disc medias for movies currently available but also can hold a tonne more data than Xbox discs uses (dvd/hddvd can't remember) therefore reducing the need to swap discs when playing RPG's or sandbox games like Grand Theft Auto.
You can also buy a PSP/Vita and transfer any purchases from the PSN Store and play on the go without having to pay again.
At the end of the day whichever way you go you will have a solid console that have plenty of games to cater your gaming needs.