It is longevity IMO. I just replaced my single ply with a 9149H double ply. We rode 5400 and the outer band blew on the trail. It did have the Phantom studs. Also have AM aluminum wheels . They wore the thin wall area molded over the reinforcement rods . Then the rods started to break and the track tore. BRP claims that the AM wheels reduce the dampening effect ( I agree ). Just for an example , another sled we have went thru the exact same conditions and abusive riding habits and that dbl ply track lasted 7100 miles. It has AM wheels, did not fail @ the reinforcement rods , we ended up tearing the lugs off little by little until the banding went from the outside. We do seem to be " tough " on sleds here at my house. Here is a pic of the where the rods started poking thru before it tore apart.