Well to throw my 2 cents into the fire, I prefer the 360. I've had all three systems, note had.
PS3 I had for 2 weeks before it completely died on me. Brand spanking new and it dies. The built in internet browser and Blu-Ray were really nice. Then it died, and I received absolutely no help from Sony. I just ended up taking it back to GameStop and demanding my money back. They obliged, never thought about buying another one. Not that it's a bad system, aside from the burn of the system death, it's just I hate that controller! Plus, many of the games just didn't resonate with me personally.
Wii, I had the Wii for well over 2 years. It eventually just sat there collecting dust. I realized quickly it wasn't been played near enough, so I gave it to my nieces to use. My brother later told me they sold it back to GameStop and bought a 360. So that's where my kindness went. The system isn't terrible, though I noticed a lot of shovel ware that was just clogging it down in the end. So many terrible games were out there that it clogged out he good ones from even being seen.
Now my 360 I've had since 360's first came out, I did however upgrade. I've experienced one RRoD, (Red Ring of Death), that killed it and I promptly sent it away to be fixed. Within a week it was back, or rather, a new 360. They decided not to fix it and just send a brand spanking new one. Which was fine since I had my Hard Drive and it took just a moment to slap it on and get back to gaming. Didn't have any further problems, when the new slim model came out, and I read some reviews, I went to the local GS and traded in my old for a new. That's what I have now. I'm not much into the Kinect crap. Never really got into the Motion Control Phase despite having a Wii. Anywho, I love my 360.
I can play all kinds of old Xbox games, I can play great XBLA games. Like the new Simpsons Arcade game, or the old X-Men arcade game. Castle Crashers, etc, a bunch of nice titles, most of them may not be exclusive but they are damn fun. Now, 360 does have it's exclusives like Gears of War, a pretty decent shooter, Halo, never been a big fan, and I think that's pretty much it. A few more show up every now and then. I can watch movies through Netflix, or one of the other random services they now have. Not to mention YouTube is finally there. Some other random things I can't remember nor really use, including ESPN, and Hulu.
All that aside though, it's what I have the most fun on. Aside from the laptop of course. The real question is, "what do you think you'll have the most fun using?"
We can give our own personal experiences all we want, fanboy or rage against a certain console/device. However, all of that is useless in the end. In the end it's your own personal decision, sure we can push you to one side or the other, but again, you should make the choice yourself. For me it's the 360, for others it can be PS3, or Wii. I have no qualms against any system or their users. Personally, I wish all this flame and hate for each system would die and we could all just get along, but since that won't happen I just have to say, "Hey that's cool man."
That aside, we've given just about all the advice we can. The choices are ultimately yours to make as you see fit. Hopefully though, we've given you some good advice to use when making that choice. If not, well, no one is perfect. That said I wish you luck on your upcoming console journey. :)