Skate: The PS3 has a pretty bad UI. There is no question, it has the worst out of the 3 consoles. It has some decent exclusives for FPS and hardcore gamers, and has by far the best potential for graphics, but it isn't really good for casual gaming. As mentioned previously, it has a blue-ray player, so if you're looking for entertainment bundled with it, the PS3 could be a good choice. Also in my experience, the HDMI cable has been a pain in the ass to set up.
The XBOX has by far the best UI. I don't know who it was that said the Kinect was bad, but that person obviously doesn't have much experience with it. I have all the motion controls for XBOX, and the PS3, and of course the Wii, and I think that the Kinect is by far the most fun. The console just has a good...feel to it. Not to say it doesn't have downsides. You have to pay a relatively high cost for Gold. The hardware also doesn't have near the potential as the PS3. I've heard a lot about bad hardware, but I've never had even the slightest problem with my XBOX. Not even a crash.
Xbox is a lot more programmer friendly.
You can compile xbox code in visual studio and the API is not flawless, but it is a good effort.
I've set up a PSP programming environment and it was a royal pain in the neck. All the components were piecemeal and they often didn't play nice with each other. Apparently, the PS3 is better, but not as good as the Xbox.
I've been told that you need to be a PS3 guru to take proper advantage of it's "avanced" hardware. In complexity, you need to go all the way down to assembly-level optimization.
Programming software is enough of an error-prone task as it is. You can come up with an architecture that has great potential for optimization, but if using it properly requires rocket science, then few people will use it well and the "powerful hardware" functionality will just go to waste.
You need to factor in how much complexity the human brain can reasonably process. The vast majority of the time, slightly less efficient, but more usable is way better.