There was a difference in traction depending on snow conditions. Stock track is better in the lighter snow. Trail, wet or mild weight snow the backcountry hooks up way better. And just to clarify I've had three tracks on my 11
1.375 cobra with stock short lug gearing, stock weights and an EPI spring, not sure on the numbers on the spring I'll have to look into that. Overall revue. Not enough track for me. Power and speed was all there
2.0 series 5.1 with stock polaris 2.0 gearing, same clutching as above. Never actually lost and power or speed from the 1.375 inch track but gained a lot of traction. Sled pushed more in the corners when on a trail. Unfortunately my sled seems to have eaten this track
1.75 backcountry, polaris stock 2 inch gearing, same clutching. By far the best all around traction, also the most push when on trails. With this set up I did actually gain a few mph over the other two set ups. I think it was 4 mph. Power and torque seemed unaffected. This track also stood up to the crappy snow conditions we has in my area last year very well (mainy freeze thaw cycles) and after 1000 miles of crap snow and dirt looks like new, Quite impressed by that
Also my roommate runs a 12 SBA with the polaris 2.4 inch, and a similar set up sled and anytime we have done a head to head I have won. Something else to consider.
Hope this helps