Sounds like you are shooting jpg only.Typically I bring both cameras in the field, if possible. However, if I have to choose one it will be the 7d. Thats because the extra pixels on the subject gives me more details and less noise after pp and downsampling of the 7d crop to the same images crop as 1d4.
Haha, what? I've had both and the 1DIV is vastly superior in every way - IQ, AF (especially tracking AF), noise handling, etc + I can crop deeper into a mkIV image without it turning into a noisy mess than I ever could with my 7D. The 7D is useless past ISO 800 imo if you intend to crop at all, which, if you are shooting birds, you will be 99.995% of the time. When I first got my 1DIV I was positively giddy at how much better the images were to work with and how much better they look. Whatever small advantage can be gained with the crop factor is absolutely steamrolled by every other aspect of the APS-H and the 1D body.
Actually, the one thing I really do miss about the 7D is the precision center AF point. That was pretty badass. I don't miss how it dropped focus every other frame in servo mode, however.
To compensate for the higher amont of pixels on the subject you need to put a extra tc on the lens on 1d4.
This will cancel out the one stop iso advantage 1d4 has vs 7d.
Also the af will be slower due 1 stop slower lens (with tc).
If You are in a reach limited situation with the 500mm + tc's and the two bodys, what combination would you use?
1d4 + 2x tc or 7d+1.4tc?
The 7d combo will win regarding details and AF speed. Noise will be equal.
Maybe you would stick with 1d4 +1.4 tc. In this case the 1d4 af will be better. 7d will have better details but more noise. However, you can easily pp the more detailed image from 7d and then downsample to show same subject size at 1d4. Again, the 7d will win. At least for isos up to somewhere betwen 1600 and 3200.
You said spot af is the only thing you miss from 7d. What about a quick way of change shooting setup from BIF mode to static mode? If you are a birder and dont miss that, I doubt you seriously have used these bodys. Or maybe you can give me a good tip
Since nobody asked it yet, I will: WTF??