The XCR shoots a lighter caliber, isn't ambidextrous, has a longer overall length (no one is going to be shooting one folded), has an inferior trigger than the RFB, has fewer gas port settings, and ultimately is not all that incredibly different than an AR15.
The XCR will shoot a 6.5 Grendel or the 6.8 SPC, which is less than the the .308, but the 6.5 Grendel has similar ballistics. I have shot a lot of .308 but after owning one assault rifle chambered for it I would not want to have to hump the extra weight and take the extra abuse day in and out. Having used the 5.56 in the Army I have no desire for a rifle chambered in that. I would be quite happy with a 6.5 Grendel.
The XCR does have ambi-safty and yes you are correct that you would not shoot it with the stock folded. Having carried the M16A2 with a 20 inch barrel I don't feel like the extra length made that much difference, thus unfolding the stock when in hostile areas would not be a big deal.
The XCR actually is quite different than the AR platform. Take a look inside of one of them and you will see that aside from the the looks of the lower and the ability to take a Ar mag, they are very different and much more reliable.
I don't know about the trigger difference on the RFB compared to the XCR. I haven't shot the RFB. Have you? If so, how do they differ?
Now if they came out with the RFB in .260 Rem I think I might bite. They also say they might make a version in 6.5 G which would be cool.
Anyways I didn't mean to get into a war about which riffle was better. I didn't say that the XCR was, just using it as a price point comparison, and I believe it is overpriced as well.
Feel free to flame me, I don't really care, I'm fireproof yo!
Best regards,
Greebe