The theory with big wheels is that the track bends around a bigger radius with the big wheel kit. Bending tighter takes more energy. The big wheeled tracks will have less energy loss which means more HP to the ground. Some guys find it pretty substantial, others not as much.
If you delete any of the bogey wheels on the suspension, seriously consider running ice scratchers when you ride on hardpack or ice. If you remove wheels and don't do the ice scratchers, you will be replacing hyfax very frequently.
2007 RMK 700, 2008 RMK 600, 1995 AC Prowler 2-up, 1980? AC Cheetah