What's the advantage of having a full system over a slip on? What will you recommend?

 

slip on is sound, full system is a few extra hp.

 

with proper tuning, full will get you more than just a few ponies...actually it'll get you a lot of peak ponies, 10 on the higher side...however, your lowend will not be as reponsive on a 600...so it's better suited for track riding.