Great question. Not sure why exactly..except that rubber has more traction than metal. Also some rubbers grip better than others on different types of materials.
Heres the SLP comments..Can your slide take the heat? Stock hifax melts at 300-325ºF, HiperFax™ melts at 750ºF. This remarkable patented material reduces heat and friction for better high speed, hard-packed or use on paddle tracks without melting. Improved fuel economy and slide rail life.
*NOTE: For models that have closed window tracks you must use anti-wear pads. If track has all the windows open yet crossbars are not clipped, clips will need to be added.
I got into an area that someone else new very well..of course he didnt have a clue how to get us all back out...snow level was very thin and icy...all were low on gas...then I was smelling hyfax...mine were fine, where stockers were starting to melt.
TIP..if you are behind someone and you smell something that is similar to the smell of parafin wax burning..thats hifax! You can stop and hand pack snow into the tunnel if you cant get into some..or an oldtimers trick when you dont have scratchers or they are not doing enough...you can "carefully" you should not attempt this at home..Lay your boot down and drag it one side at a time at an angle that will shoot the snow into the track.
Simmons skis have a dual outside carbide that sprays a lot into the track..stock skis on the Polaris are barely on the snow and dont spray squat. ON simmons skis you can add little SS deflectors. I have them they work great. Do not get the steel ones they suckh. the Stainless ones last forever.