Canon VS Nikon VS Sony DSLR Help?

Of the Nikon's, the D7000 will give you the most options As a rock climber, the 10-24 mm is the wide angle lens that will provide you with the most amazing landscapes Shooting at the track, either the 18-200 mm (best for shooting motocross from within the track) and 24-70 shooting dragsters and 300 mm for shooting oval track races.

Have you tried Pentax ? Seriously, find a dealer who'll let you handle them. It's the only way.

I think you are going to have to just read the reviews and weight the features of each camera on your own. Other photographers (myself included) have answered this type of question every single day, for years now. If you search here, you will find more answers than you know what to do with. In the end, too many people point buyers toward Canon or Nikon, telling them how great each one is, and always forgetting to mention the cons. For rock climbing, you might be better off with a GoPro, and just use a high quality large sensor, compact for clear stills like a Sony NEX 5N, a micro four thirds from Panasonic, or Olympus, maybe even a NX200 from Samsung, or J1 from Nikon. If you want a dSLR that can take more of a beating, and you plan on keeping it for the long haul rather than update it every 18-24 months, go for a mid-range dSLR with a mag alloy body, they tend to have some kind of weather sealing, and the shutters actually get rated. Since Sony just released the A77, you might go that way with them. Nikon's D7000 is sweet, but getting a tad old, it might get an update in the next few months, same for the mag alloy body Canon 7D. A Pentax K-5 is a rugged camera, well reviewed, mag alloy body with Sony's sweet 16 image sensor, they managed to squeeze more from that image sensor than Sony (with the A580) or Nikon (D7000). Cameras like Nikon's 3100/5100, Canon T3i, and even Sony's amazing new A57 with tons of features and abilities are too plastic-y with no weather sealing, so I would not recommend them for rock climbing, temp extremes, possible misty/rain conditions, high heat, high altitudes etc.

Considering brands only; you are best advised to visit a camera shop and handle the things. How do they handle, are the buttons in the right place your fat/thin fingers? Too heavy, too light? As a Nikon user I'll comment on those listed in your question. The D5100 and D7000 outclass both the D3100 and (sadly) the D90 in quality of capture. The D5100 and D7000 carry the same excellent sensor, so the price difference is all about bells and whistles. Is the convenience of the extra (useful) buttons worth the price difference to you? You'll be taking the same photos. The Sonys; I read good things about their quality and have the impression that you get a lot more for your money compared to the big two, you aren't paying for the brand. (But, I won't be switching from Nikon, personal preference.)