So I looked into this before buying my CII.
- The R comes with the grip/extension plate (I've added a 3rd party one to my CII for bigger lens use).
- The CII is rated for a bit more battery life.
- The CII has slightly more phase detect focus points.
- The CII is a bit faster (more FPS)
- The CII is significantly lighter on the wallet
There are probably video differences too but it's of less interest to me so I don't know them. I don't worry about 1 card slot, never had a situation where I've been glad of 2 (touch wood). And at the end of the day, this isn't a pro tool for me, it's a hobby, and I accept there are sacrifices for a compact body.
For me, there's less advantage in the R if you're not shooting top quality glass - I see a lot of GM in your sig though! That said, for me, the main appeal of the compact body is compact lenses, which _tend_ not to be as good. Certainly for my uses, I'm happy with the 33MP and 14Mp shooting crop lenses.