I have copied the text from Axon's site concerning the difference between the lenses. The outdoor lenses are basically slightly darker than the indoor ones.
"Lenses: Axon offers two different tint densities for you to choose from: Indoor, which is lighter; and Outdoor, which is darker. See pictures of the different tints by clicking here (opens new window). Transitions lenses® have our indoor tint when inside a building or car, but turn dark when in the sun. Our Polarized lenses are Extra Dark because they use our outdoor tint with polarization – they appear dark grey. Polarized Lenses are available by special order only.