My thoughts as owner of too many cameras.
1Dx II -- Used almost exclusively for sports. None of my other cameras match it for sports. But, it is not perfect. Autofocus could be improved and it could use more resolution. It looks like the Mark III will improve the autofocus and I hope it will improve the resolution. Frankly, if they took the 30 mp sensor of the 5DIV and R and put it into the 1Dx, I'd be happy. Still, despite whatever weaknesses it has it is absolutely the best for fast action. It is absolutely the worst choice for situations that require you to be unobtrusive. The "silent" shutter is a joke.
There are tons of little niceties with the 1D series that I tend to forget about until I try to find them on another camera – The ability to download all your settings to a card so that you don't have to redo them after it's been in the shop is one example. The complete customization of the "Q" screen is another.
5DIV -- Great all-around camera. It can be used for action, but not quite up to the 1Dx due to the lower fps. Great for events, especially when you need to be discrete. The "silent" shutter isn't silent of course, but quieter than 1Dx by several multiples. The 30mp sensor of the 5D and R perform as well at high ISO as the 20 mp sensor of the 1Dx. For birds and
and wildlife I actually prefer the 5DIV to the 1Dx II because I feel the extra resolution of the sensor outweighs the slower fps. Autofocus is essentially the same as the 1Dx II.
R – Over the past few months this has become my main camera, displacing the 5DIV in most cases. I have really come to love the ability to move autofocus points around using my thumb. I like it for portraits because I can nail the eyes much easier with it. For events, I feel that with the touch screen autofocus point selection it is more responsive. Also, if you need a truly silent mode, the silent shooting is actually kind of creepy it is so truly silent.
I really feel like the R has improved my composition, because I can quickly move the focus point anywhere I want. Instead of composing a shot based on where the focus points happen to be available, I can compose the shot and move the focus points to match.
Works pretty well with birds in flight and wildlife, with some notable exceptions. With birds in flight, it can hunt for focus, causing you to miss shots. When it does find focus, it locks on very well.
What’s not to like: I can’t get the hang of using it for sports. It’s not responsive enough for my tastes and the teeny-tiny back-button focus button is impossible to find consistently.
The tiny buttons on back also mean I find myself accidentally changing the various focus selection modes at inconvenient times.
The touch bar is kind of useless to me and in fact, when I have tried to use it, I found it to be a bit buggy, working sometimes and not at other times.
The firmware update improved the eye autofocus, but not well enough to work if you are shooting more than one subject. In sports shooting, it will move off the selected subject and find another player’s eyes/face making it unreliable.
The single point selection box is too big in some case and it could use the additional smaller point that can be found on the 1Dx, 7DII and 5DIV.
7DII – I mention this only as a point of comparison and a bit of nostalgia for a body that Canon seems to have killed off prematurely. In short it has almost all the benefits of the 1Dx II in a crop body. I still find myself gravitating to the 7DII if I'm shooting birds in good light. That said, I've found that the extra cropping allowed by the 30mp sensors of the 5DIV and R compensate a bit.
What good is this to you?
There is no one camera to rule them all. If you don't shoot sports, birds in flight or other fast-moving subjects, I'd recommend the R with no hesitation.If you really want the best Canon has to offer, shoot action and never need to shoot meetings or other venues where discretion is needed, the 1D series won't disappoint.