Comparing ACR Process 2012 for 5D2 and 5D3 though I'm not seeing the detail advantage for the 5D3. With Neutral +4 sharpended, 0 NR in cam jpgs the 5D3 ones at ISO100 showed definitely more and crisper grabbed detail actually. Using ACR with all settings to 0, I can't see much, maybe 5D2 is a hair crisper per pixel but 5D3 has a hair more pixels, seems pretty similar detail and all between them.
Yeah at ISO100 honestly can't see much between the 5D2 and 5D3 for captured detail using ACR. So I don't see anything to match those saying it pulls in noticeably more detail than the 5D2. OTOH I definitely don't see anything to match those saying the 5D3 is soft and no good either. Honestly they seem pretty much the same using ACR, in that regard. Using in cam jpg neutral profil at +4 sharpening and 0 NR the 5D3 jpgs have less moire/artifacting and pull more detail than 5D2, at least for areas of very strong contrast (it might be the 5D3 fuzzes over low contrast detail more with in cam jpgs, at least with certain profile, didn't check that here though).
When reach limited 5D2/5D3 seem awfully similar but the 7D very clearly brings in much more detail than either.
And yes the 7D holds a clear advantage over the 5D2 when reach limited under any circumstance. Even at ISO6400 it pulls in noticeably more detail and if you normalize, even just using the simplest method, size of captured object between them the 7D delivers it with LESS noise and much less artifacting and more detail. Hands down 7D beats 5D2 when you are reach limited whether you shoot ISO100 or ISO6400. Compared to the 5D3 it also hands down pulls in more detail at ISO6400, however, in this case, if you compare them at same target size scale it doesn't have a noise advtange over the 5D3, it's a bit worse, although the detail is still a touch better and with less artifacting from debayer for sure. So I'd still say the 7D wins over the 5D3 too when you are reach limited be it ISO100 or ISO6400, although by a lesser amount at ISO6400.
All compared at 8MP, a non-reach limited comparison, the 5D3 looks cleanest at ISO6400 and then the 5D2 and then the 7D.
But note that this was a quick test, the raw converter profiles and on didn't apply the same color balance even after hitting white point tool on same point and so on at all and the exposures for same setting varied for each camera. At ISO6400 5D3 exposed the most, 7D the least. Didn't normalize for that at all.