I have 2 scope with 30 mm tubes and don’t find much of an advantage over the 1” tube although they are not top of the line scopes. One scope is the Leupold Euro and found out the internal parts are the same as the 1” tube. I’m not sure if this applies to the VX-III series.

The scope in question with the 30 mm tube has more adjustment in elevation for long range shooting and is slightly heavier by 0.4 oz. I also find the 30 mm scope to be a little more bulky and you do need new rings if you had intentions of using existing rings. What I like about 2 of the three scopes is no Adj. Obj. lens. Just one more thing that you don’t have to worry about when hunting. Good luck in your choice and take a look at the Zeiss Conquest if you have the opportunity...