is it better to use bigger gears for less rolling resistance, or smaller gears for less rotating weight??

That question is sure to cause some debate. It's my understanding that current thinking has the larger gears delivering more horsepower to the dyno....and I guess that's what counts?

what do you gear for 1:1 or full shift (.75:1,1:1.33)?

The ratio is all that really matters. The difference in size/weight of bigger or smaller gear that would fit in a chaincase wouldn't make much if any difference. Full shift depend on what primary and secondary your using. Skidoo is full shift at .83:1, most other brands are full shift at 1:1.

smaller top gear brakes tooth easy, go for a big gear in top....and a bottom that matches it of corse. :lookaround:
Lars