I agonized over the RP vs. the EOS R. I decided on the EOS R. I get it today!! Excited.
The reasons that swayed me were:
-RP not out at the time
-RP does NOT do silent shutter (hope they do in a future firmware update, how this is held back blows my mind)
-R shutter is rated to 200k cycles. RP is 100k. (not a huge deal, but it did help sway me)
-R has noticably better dynamic range and shadow recovery. Used to shoot the 6D and 5DII and shadow recovery was always nasty.
-R uses a bigger battery
I do like the way the RP looks with the grip, and its smaller size. But really when it came down to it, I love the ability to shoot silently.
I have a feeling I won't like the mode dial on the R. I like the traditional mode dial since I switch between TV and AV a lot. I like being able to switch on the fly. No idea how I'll do with the R. I'm sure it's possible.. just not sure if it's as fluid as turning a knob.