ironfreak said:
My dream of owning latest Canon ff body has been shattered.... :-[ I cannot wait till Sept and cannot afford 1DXM2 .. I have to move do Nikon system with D810!
It really depends on how much glass you have invested / mount system.
However, if you are going for speed, then, there really isn't a choice for a new generation full frame pro-series camera, since the D5 is $1K more expensive than the 1Dx MII (which is less expensive for a faster shutter).
If you can make the switch, then Nikon has a very good line-up of new cameras that makes it extremely competitive in the later part of this decade. 3rd party glass manufacturers like Sigma and Tamron make Nikon mounts for all of their lenses, so you will not have compromised quality over price for a more constrained budget. Nikon has caught up in many aspects (the new D500 beats the 7D Mark II in several categories, and the new D5 finally achieved maturity on MP, ISO values, AF tracking, and shutter speed). However, Canon continues to deliver on their professional equipment with ideal quality and value innovative engineering, albeit the slower turn-around rate of new bodies (1D, 5D, 6D, 7D series) to the general public.
I too own the D810 and love shooting with it. It is a dream camera. However, a clear disadvantage is the slow 3D tracking. It is not as fast as the 7D Mark II, 1Dx, or 5D Mark III's quick point tracking system. At least the point change speed and fast change AF groups can be customized with those Canon cameras. Also, the button placement for ISO, WB, and AF tracking is awkwardly positioned. On off switch can be tricky, so be careful not to accidentally bump it, or you may turn your camera back on in the bag. Not positioned near the trigger finger, and not ideal for quick hand movements. I am getting "used" to it, but it could have been engineered differently.
Obvious advantages of the D810: reasonable price for the combined features of a very quiet shutter, extremely high resolution (7K), battery life (just like a 1Dx battery), ISO's below 50 (and options other than 100 in the low range), 3 crop modes (which give faster speeds up to 7fps), higher retention of clarity / resolving power at higher ISOs, no low pass filter, and many more features.
All the best!