HH exhaust has a slightly larger diameter pipe, and has a spark arrester, which is important if you ride on any public lands. The HH is also a simpler pipe, where the MRP is fairly convoluted and sometimes requires relocating the electrical box (depending on where it is on your buggy...)
The exhausts themselves are fairly close to the same in overall performance with the edge going to the HH.
You'd probably use a 130 to 135 jet depending on your elevation, but you're never going to beat a quad - period. Your smaller engine and significantly higher vehicle weight will see to that.
BUT, you can run him off the road easier!
