@mr-quebec, if you’re going for wildlife, then you’ll always wish you had a longer lens than 200mm. Even on a APS-C sensor, 200mm just doesn’t reach far enough. If you haven’t already made a decision, I would go with the 300mm, determine it’s sharpest zone (with both aperture and shutter speed), and do your best to stay within that range when you’re using it. While sharpening using software is never a good substitute for using a sharp lens, it’s better quality, I think, to zoom in instead of crop.
I did some indoor tests and this is what I came up with :
Autofocus : fine but a bit slow
IS : quite good, just noisy
Sharpness : That’s the one I care the most. The pictures tend to be soft, but sharpness greatly improve when narrowing the aperture. Picture quality seems great at f/8 or f/9. Since I plan to use that lens for wildlife, it’s not a big problem for me, since I have generally enough light to work with.