I only have a 360, and I love it. No Kinect for me though, the family has a Wii if I really want to play something like that. Lots of the games are coming out "enhanced" for the Kinect but you don't have to have one for them to work. I know my Xbox is connected via the component cables... I thought the new ones all shit with HDMI cables and HDMI output, but they might accept the component cables as well, just check best buys site and it should tell you right there. You can also get the "older" non-slim model, its basically the same just in a little different case.
I think they both ship with component and hdmi cables, so you can use component cables for a non hd tv. In most peoples opinion xbox has sony beat with game selection, but ps3 with more sophisticated game engine and blue ray technology means better graphics and more memory per disc, as well as the option to watch blue rays on it.
As far as motion gaming I know a lot of people complain about kinect not being as sensitive or accurate with the controls as you would like, and theres not much of a game selection. If you want to go the motion route youre better off just getting a Wii in my opinion.
Thing is though, it looks like the next generation of console is just around the corner, with nintendo already showing off new concepts and hardware for their next one (they usually come out a bit before the other two)