Tom,
The only two real advantages of 30mm scope tubes is they're somewhat stronger than 1" tubes, everything else being equal, and allow for more adjustment range, which became important when turret-twisting became important.
There is even an exception to that, however. For many years Swarovski insisted on putting bigger lenses inside their 30mm scopes, resulting in no more adjustment range than comparable 1" scopes. The bigger lenses do have relatively minor optical advantages, but still don't increase exit pupil diameter because (again) that's determined by objective lens diameter and magnification.
