This is what's happening with me. I would really like a FF backup to my 5Ds that can handle video. I've passed on the R and now the RP. I really don't like the idea of dealing with Sony's UI or non-native lens adapters, plus Sony bodies are useless in poor weather. But when is Canon going to deliver decent video specs?To be honest, I really want this EOS-R for photography, but I'm not going to buy one because it's another piece of equipment that can't double in video, so I would most often leave it at home.
Dynamic range I could care less about, and I shoot scenes (including occasional real estate interiors) that should put me in the category of caring greatly about it. I know what I can do with the 5Ds sensor, I know how narrow the DR band actually is between the 5Ds and Sony sensors, and I know how to handle the scenes that exceed any sensor's DR.
But video...the other guys are doing oversampled 4k footage (generally 6k-to-4k) that looks beautiful. They do this with their best AF modes enabled and with no stupid restrictions on frame rates. And with Sony they do this in FF mode for low light situations.
The more I think about it, the more I wish Canon had used the 1DX2 sensor in the R, the RP, or both. Until they get their readout speeds figured out they need a solid FF video camera.