all i am interested in is image quality....so after getting the 5DII, i sold the 1dsIII as fast as possible....the 1ds has much better af, the body is weatherproof and all that....the 5DII is much smaller, lighter....and it has much better high iso and (most important for me) the DR at higher iso is in a different league.....i would say the 5DII has an extra 1.5 stops at 800iso....and less noise......i don't see either one having more detail at 100 and i do miss the larger finder of the ds....but like i said, i am interested in image quality so the 5DII wins for me...the video is purely extra....i could not care less what "professionals" use...i have the grip but actually almost never use it....not sure why i should make the camera bigger and heavier then necessary....
I like the 5d2, it shoots a great still, pretty good video, etc. etc. I don't notice the viewfinder that much, but I completely love the 1ds3's. The focus on the 3's could be a little better, past 800 iso is a challange, though up to 640 I see no difference between that and 200 iso.
I think the 1ds3 produces amazing skintones, which is really the reason I keep them and since owning them I've shot about 50 medium format frames, 50 billion 1ds3 frames. It's that good, imo.
When the 5d2 came out I thought about selingl both of my 3's but at this point they're not going for that much used and they tether well with eos utility, so I thought I'd just keep them.
I guess in a way I could just carry 5d2's and be done with it but the 1d3's are paid for I know all the buttons and switches and I only use my 5d2 for video anyway, so . . . today I'll keep them.
JR