You'll be paying a bit more than $1015 for an LMT in the US. Just to get a functioning rifle you'd need the parts listed prior, plus:
-BCG $140
-charging handle $25-90
-some type of rear sight $140
-some type of handguards $35-infinity
As far as an SBR AR goes, $1499 is pretty damn good for any sort of complete rifle, even here. If its the last one available in the country, its an absolute no brainer; what are you waiting for?
RRA in general; they aren't up to the milspec standards of LMT, but they aren't bad rifles either, and if you just replace the RRA BCG with an LMT from day one, which is a pretty cheap proposition, you will have fixed 75% of the RRA shortcomings in one shot. I would think. That would be true on a 16" rifle, at least. I'd also change out the buffer for an H2.
10.5" AR uppers in general are.. eh... "high strung" and have a reputation for being finickey and needing to be built just right to run correctly. My 10.5" LMT has never had a problem, but I have no experience and have never really heard anything at all, good or bad, about a 10.5" RRA. Actually I didn't even know they made one. The LMT version has the gas port expanded just a hair over that in a 14.5 or 16" barrel.