Thanks, neuroanatomist for your analysis. (Might I surmise, both from your name and the substance of your posts, that's something you do best?)
Part of my day job.
Though, I would have thought the 7d might have been a better performer than the 1DS3 in real-life, action situations (given that it has both a newer sensor and processor) and maybe up there on the level of the 1D4.
Age isn't everything. Canon's 1-series bodies historically get better AI Servo algorithms (the 5DIII is a departure), and also the 1DsIII has f/2.8 points scattered across the frame whereas the 7D only has the more accurate f/2.8 at the center point. Those factors lead me to rank the 1DsIII above the 7D.
Another thing to keep in mind is that with the same lens, 1-series bodies focus faster than other bodies because the battery delivers a higher voltage, which drives the lens' AF motor faster (and a battery grip on a non-1-series doesn't help since the batteries are used alternately, not simultaneously).
What I'd also like to know, as well, is which lenses work best on a given body. Say, compared to my 300/2.8 (not the latest II model), how do the following rank up: 300mm f:4 (IS and non-IS), 400/2.8 (both I and II), 400/4 DO and the 500/4?
I'd approximately rank them as 300/2.8 IS II = 400/2.8 IS II > 300/2.8 IS = 400/2.8 IS > 500/4 > 400/4 DO > 300/4 IS = 300/4 non-IS.
That's splitting hairs - in real-world terms, you'd likely not notice a meaningful difference between any of the supertele lenses, and the 300/4's would be a little slower.
Also, I'd be interested in seeing how much effect the 1.4 and 2x converters have upon their focusing results, a little or a lot and do they affect some lenses more than others. And, does anyone notice any speed/accuracy distinctions betwen the II and III models?
The 1.4x TC slows AF by 50%, the 2x TC slows it by 75%. Overall, the MkIII TC's are supposedly a little more accurate than the MkII's, but probably not relevant in acutal use.
And, just where would the 70-200?2.8 IS II fall in, by itself and with the converters?
The bare lens would likely slot in just behind the supertele primes for AF speed, a little faster than the 300/4. TCs would have the same effects (50% and 75% slower).
In terms of 'overall' AF performance, I'd stack rank the recent bodies as follows: 1D X > 5DIII > 1DIV > 1DsIII > 7D > 60/50/40D > 5DII > xxxD.
I'd agree with that.
5d3 sealing is improved upon compared with 5d2.
Yep. Relative weather sealing is: 1-series >> 5DIII = 7D > 5DII = 50D/60D.