Re: Semi 308 WIN
Every platform has its advantages and disadvantages and I certainly don't think that the Armalite is necessarily "the best." It is an excellent rifle that is capable of great reliability and accuracy depending on the ammo/shooter. I have owned an AR-10T for several years and while it doesn't get used as much these days because I have too many other 308 gas guns, it is 3/4 MOA capable with handloads/match ammo and when I am doing my part.
Besides the Armalite AR-10 type rifles, you should also consider the DPMS LR-308 (various configs, etc. depending on your needs).
The primary differences between the two platforms are the mags and the differences in dimensions on the lowers/uppers. The Armalite rifles run Armalite mags only (based off the M14 mags). The DPMS run a different mag setup based off the Knight's Armament SR-25. Unlike Armalite, there are nmumerous sources for mags, including DPMS, KAC, C-Products, and eventually Magpul (likely after the first of the year).
I would pass on the RRA. Not saying that it is a bad rifle, but they are highly proprietary rifles that the "aftermarket" doesn't seem to be interested in supporting. The only real "advantage" (if you want to call it that) is that the RRA uses FAL mags which are plentiful and fairly inexpensive compared to $45 Armalite mags.
As for the Remington R-25, it is based on the DPMS platform, using the same upper/lower/barrel nut/mags/etc. They are fine rifles for the money, but I'd go with a DPMS.