2 or 3 years of experience?
RRA was started (by most accounts) by ex-Armalite employees. Armalite has plenty more experience with ARs than Bushmaster (AR stands for...)
Personally,I find Rock River Arms to be superior to Bushmaster in a multitude of ways. The fit is typically perfect, and the finish is a consistant dark BLACK (not purple). The barrels are of very good quality, and shoot very well; Bushmaster barrels are chromed and shoot decently. If one desires the chrome, it costs $50 more; a portion of the $200-300 premium for the Bushmaster. Also, the Rock River Arms NM trigger, standard on many models, is an incredible piece of machinery. This costs $100 extra if you want to buy one for your bushmaster.
Lastly, if you buy RRA, you help bring competition to the market, which means more choices and lower prices.
I'd go for the RRA.