Wildlife photography, some doubts?

Actually I wad thinking of buying a camera body Nikon d800 or mark iii, but I'm too confused, gone through many reviews but yet confused for the focusing speed of both the cameras but one thing is bugging me that nikon d800 would give me a good quality of hardcopy even after cropping but will i get the same using markiii. Which would be best in comparison "d800 or markiii".

Have you visited the DXOmark website?

Some of your questions will be answered there, especially when it comes to dynamic range of the sensor.

http://www.dxomark.com/...nd2)/Nikon

How fast the cameras can focus have a lot to do with the lenses you buy.

Nikon AF-S and Canon USM lenses are the fastest focusing lenses in they stable of lenses

What many wildlife photographers do is use cropped sensor cameras to get extra reach with their 300 mm f/2.8 and 400 mm f/2.8. The reason of using fast lenses when shooting wildlife is because they are most active during dawn and dusk, so lighting can be a problem.

The Nikon D800 allows the photographer to use the equivalent of a cropped frame camera as one of its features. When you do this, you still see the full frame (greyed out) and the cropped section to show what the camera is recording. This is especially helpful when shooting running animals. I use the same feature when shooting motocross and other action assignments