I have a snowchecked Axys 163" with 3" lug, and my wife has the in season Axys 163" with 2.6" lug both set up identical. I've got around 1,300 miles on the 3" lug, and her sled has about 400 miles. I've obviously ridden my 3" lug more then her 2.6, but if you didn't tell me which I was on I honestly couldn't tell you the difference. I would have to assume if the 2.6 just barely got stuck at the crest of a hill, the 3" would make it and I'd be glad I had the 3". Would the 3" barely pull away from the 2.6 on a deep day... yeah I guess, but again I really don't think anyone could tell the difference if they didn't know which one they were on in any given situation.
The other difference is the chain vs. belt drive? Again, I really can't tell the difference there either. Give both sleds to anyone to compare and don't tell them which one there on (belt or chain / 3" or 2.6") and I'd be willing to bet some $ most riders couldn't tell the difference with any thing other then luck. I'd love to see the equivalent to a blind taste test for both the 3" vs 2.6", and the chain vs belt on any given day. IMO most riders wouldn't guess right...
As far as trenching... same opinion as above. Give most riders a blind taste test and IMO they would not be able to come back and say with 100% certainty "yeah, that sled was without question the 3" cause it trenched more" etc... Again just my opinion...