Since I am trying to amass opinions everywhere else, why not, right?
Due to some unfortunate circumstances, I had to sell my 500 a few months ago. My Sigma 120-300 OS with TCs has been filling the spot since and has done an admirable job. However, with fall and winter right around the corner, I am convinced that while it could a wonderful job with the 1.4 on waterfowl, that's gonna leave me lacking some reach.
So, I am going to pick up another super. 500s and 600s are running the same price, 400 2.8 slightly less. As this will be mated to a tripod and gimbal head and I have very short hikes required in my area, weight is truly not an issue - so rule it out.
The 400 draws me because it can handle both TCs well, giving me 400 2.8, 560 f4 and 800 5.6, if needed. The 600 gives a little more reach vs the 500, at a similar cost. And the 500, well, we all know it is awesome.
So, I am a little stumped as to where to head in my search. Keeping in mind that weight is ruled out and the lens will be mated to a 7d for BIFs and lare mammals (deer, bears, elk, so on), which would you choose and why?