It all depends on what you want out of the bike..
If you want it coming on strong off the bottom but signing off early up top, go with Rockets.
If you want to lose a little on the bottom but want it pulling longer on top, go with Shearer.
For MX and trails, I would opt for Rockets.
For open dunes, I would opt for Shearer.
There's a chance that Sniper may be the best pipe for that motor, but we haven't done the testing on a 4mm Serval yet.