For the most part, the MR1 is a slightly tacticooled hunting semi. They're light, reliable and accurate. Controls are anal. Aftermarket is limited to what you can bolt onto the top rail and front tri-rail available for them. The XCR was designed with military contracts in mind. Controls are very similar to an AR aside from the charging handle and bolt release, both of which are good designs. Reliability is excellent but dependant on quality magazines. Kinda goes for everything mag fed though. Accuracy of newer XCR's are excellent. If looking at used, be aware that the older they are the crappier they are. Look for an ambi mag release to be sure you're getting one from a solid revision. You can send the serial # to RA or Wolverine Supplies to get the year of mfr. and revision. Don't pay top dollar for an old one. The heavy bbl XCRs are a little front heavy if you're not man enough. The gym has an effective fix for that. The light barrels are nicely balanced.