Cant go wrong with either. I had an RPI setup on my M3 and loved it. RPI makes some good quality products. I chose Meisterschaft for my M5 because they offered the remote valves which was important to me. I absolutely love this feature. Oh, and the 102mm tips dont suck either. Sound is similar for both systems and I would bet the power increase is similar as well.
2015 F86 X6M
2015 i3-REX- 2012 Wrangler Unlimited