Shilen30
What Jon Jackoviak posted is partially true in my openion.
The advantages of the 30mm over the 1 inch tubes are stronger build and more dial adjustment. Also more room for add ons like side wheel parallex and reticle illumination.
Light will travel through a 1 inch tube as efficently as a 30mm tube, so no advantage there. There may be a false perception among the shooting community that the 30mm tubes are more light efficient but this may be due to the fact that 30mm scopes are usually more expensive than 1 inch scopes, and thus may be built using better glass. This, of course, is not always the case.
Rgds
700