I have an 03 Prarie 650 4x4. I'm getting one of 2 mufflers, both HMF. Does anyone have any insight on the difference between the Penland Pro Series and the Utilitiy Series? The only difference that I've seen is the price and that's only $15 (Penland Pro Series)

 

Both have 304 stainless steel headers and inlets, T-6061 aerospace grade aluminum canister, TIG welded aluminum brackets, can accept USFS approved spark arrestor, etc.
However, the core can be easily changed on the Pro series for different restriction/dB depending where you ride your quad (louder for track and quieter for public land).