I'm pretty sure they do have more surface area than a powder sled. The rear tracks are 14" wide each x around 42" long (contact area). Front tracks are 12" wide x around 30" long. Total of around 1,896 square inches. Figuring 900 pounds for machine (Yamaha Kodiak) and rider puts it right around .47. One of the best things about it is that you can stop, backup, etc. and not have to worry about it burying itself. Just before I bought my tracks I took a Polaris RMK with a 154" (I think) track up to my cabin and got stuck 4 times. The road is too narrow to be able to turn around when the sled started to sink, and steep enough that if I stopped or slowed down on the hill there was no getting started again. With the tracks I can crawl along as slow as I want, stop, etc. and then start going again. Not anywhere close to as fast as a sled, but for getting from point A to B with the added ability of carrying cargo, people, etc. I don't think the tracks can be beat.
I really need to upgrade to the UTV tracks for my Rhino - they have 2,400 inches of contact area