The SIG 716 uses the SR25/DPMS LR308 mags, the LAR8 uses FAL mags...
I would buy the SIG over RRA in a heart beat. Actually, I did.
I felt the product refinement and overall quality of the build was higher on the SIG. Both are boat anchors, especially after you dress them up with glass. In all honesty the SCAR17 knocks the socks off of both of these guns.