Another thing that I recall is that, all else being equal, fixed scopes are brighter than variable scopes. The reason for this, from what I understand, is as follows:
When you hear of companies, like Bushnell, that say that the Elite 4200 has 95% light transmission, you should know that that means "per lens." As such, if you have 10 lenses at 95% vs. 8 lenses at 95%, then the scope with 8 lenses will be "brighter" than the scope with 10 lenses. This is relevant because, again, from what I understand, fixed scopes have fewer lenses than variable scopes.
Zachary