A larger diameter tube can use larger lenses and has greater potential than a small tube. Price, length, weight and adjustability are clues to what is inside.
Krampus
get rings that fit 30mm and get step down adapters that fit 1"
the quality of the scope and lenses/coating outweigh the difference of the tube size
quality > quantity/size
I went with a vx3i 1-5 on my 10.5" pistol because I wanted something really light weight. It get gathers tons of light and I don’t mind the 1" tube at all. Its better than my cheaper PA 30mm.