They are both great systems, but it comes down to two things basically: online gaming and DVDs . If you want free, not as competitive online gaming then PS3. If you want more reliable online but are willing to pay for it then Xbox 360. If you own blue-ray discs then go with PS3 cause of the better value with the built in blue ray player. I also feel PS3 has better graphics for that reason. I have both systems though and Xbox 360 has alot more games.
Depends on what your gonna use it for? Xbox has a much better online base, with apps that stream everything from, Netflix, Hulu, to HBO, and can stream your on demand from your Cable Provider. I don't have T.V. anymore because of my Xbox's streaming capabilities. You can even party up with friends and watch Netflix movies together in groups. It will even connect to your window PC and stream movies/music from there. They both have great games, but its easier to play online with your friends on Xbox in my opinion, because every game is made, from the ground up, to integrate with Xbox Live. The PS3 has better hardware and Blu-ray drive which should help it last longer as far as, a next gen console coming out, to replace it. When my friends argue with me about the PS3 being better, they just don't have as many features to brag about as I do. Look at the Capabilities of each, and which one fits your needs best :)