Apples and Oranges. RRA is a 20" 1/8 twist with no sights and a fixed stock guaranteed to shoot sub MOA groups at 100M. S&W is a 16" 1/9 twist with 6 position collapsable stock, Troy Industries BUIS on "A" models, and will shoot sub MOA groups at 100M and 200M after 3k rounds downrange.
http://www.shootingtimes.com/longgun_reviews/swmp15_121906/index.html
If you plan on punching paper at 100M-300M, then either rifle will be more than accurate with the appropriate ammunition. If you plan on moving out to 600M, then you won't be satisfied with a 16" tube. I would buy the M&P, sell the Troy sights if you don't want them ($125), sell the 6 position stock ($75), replace with a fixed unit, then take the $200 I saved and have nice start to a new target scope. All in what you want the rifle to do though.
http://www.shootingtimes.com/longgun_reviews/swmp15_121906/index.html
If you plan on punching paper at 100M-300M, then either rifle will be more than accurate with the appropriate ammunition. If you plan on moving out to 600M, then you won't be satisfied with a 16" tube. I would buy the M&P, sell the Troy sights if you don't want them ($125), sell the 6 position stock ($75), replace with a fixed unit, then take the $200 I saved and have nice start to a new target scope. All in what you want the rifle to do though.