Armando, I've always really enjoyed your images and admired your abilities as a Photographer. I do not think 'which' camera matters that much
. I think I was fortunate that the gods conspired against me when I tried very hard to buy a D800 when it was first available.
I've never been truly happy with any of my Nikons after the D300,300s, and D3s. Love the files from the D700 but heavy camera w/wo grip. I've never been very happy with some of the changes to the controls. I've gotten used to not having the Focus Selector and the implementation of VR but when I take the D300s and D3S out to shoot it is like a favourite pair of shoes
The D610 is a good camera but I did not like the 39 pts. I have had zero problems with the D750 but 1/4000 is a bit silly. I shoot fast birds in good light at 1/4000 and am still at iso 400-640 but would really want faster , even as the iso climbs. The D7100 is a good camera handles whites better than any of my cameras. A bit of banding if you really over extended, and lousy Buffer but seems all of my lenses need fine tuning. Still waiting on some personal comments from friends on the D7200 but probably not in my future.
I really cannot afford to buy the D4s and a waste of time with my limited abilities and the fact that the D3S is still a great camera. The D810 seems to be the best all rounder at the moment but I opted for the D750 and saved the $1000. Also, a good friend reviewed both the D750 and D810 and recommended the D750 for me ( he knows me and my shooting well ...lol) .
The Df is another story. I did not buy it to shoot birds and Sport ( but have done
) . My only complaint with the Df is, that for how I use it, I would love to have a well spread 51 pts.
New system: I enjoy the EM1 and am getting to know it better but there is just something about the images that fall short of my Nikons. I guess the best way to describe it is they just do not seem to have the depth, not exactly flat, but just not up to the Nikons. I will not invest any more in the system. My wife really is enjoying her EM1 and has given her much more desire to get better and learn. Going to the EM1 from her Nikons is sort of like me getting the Df
. She loves the fact that she nails the focus with the EM1 and always had trouble trusting her Nikon green dots . Sony I've never trusted. A highly innovative company but never seems to do anything with their products for the long term. If I had lots of money I would like to try Fuji but not as a Nikon replacement.
I agree with Bear that there is no perfect camera. I think you could do wonders with any number of cameras, brands. Maybe think about taking a step back in technology to find what you are comfortable with. Start a local Club where everyone shoots with each others gear on outings and then you could have a 'cheap' way of trying everything
. Too bad we are not in the US where people seem to buy stuff , shoot it like hell during the return period, and then swapping for something else
. I find that personally abhorrent and am glad that some establishments have started their "Black Lists".
Take your D800 to someone very good, get a quote for refurb and then do a cost/benefit analysis on getting a new camera.
ps I've sort of had some fair winds recently to move me out of the doldrums but I feel a trip is needed to really get me under full speed
.
Cheers and all the best,
Tom