The differences with the XCR-L and the AR platform you have already covered but I was in the same boat as you when I started looking for a Black rifle to fill an itch never scratched a few years ago and decided on the XCR. I have to say too that all the options available to you now were Not there when I bought my XCR and improvements have been made since then.
1- Piston system. Easy to clean. Potential to be very reliable.
2- Caliber changes are easy and somewhat inexpensive.
But match grade barrels are Not available, only barrels from RA can be bought with any consistency. So if later you are looking for 1 MOA @ 100 yards you may be disappointed, unless you are lucky and get a rifle that shoots like that.
The things you will have to consider are that RA is a smaller company, so spare parts you may want to buy some, the reputation of RA's customer service on here and elsewhere (hopefully it is getting better) but if you go through Kermit it will be a lot easier on you if you have an issue.