I realize the bigger tube has a greater adjustment range but does it really transfer more light?

According to Zeiss' sales representative in Norway, and this woman knows optics, there's no noticeable difference in light transmission in 30mm tubes vs 1". As the light passing through the tube is a aprox 3-4mm in diameter it wouldn't really matter whether you have 1", 26mm, 30mm or 34mm...

And according to Swarovski, they could make a scope with a 19mm tube with the same light transmission as on their 30mm scopes. A friend of mine has been at some course at the Swarovski plant in Tirol, three times, I believe - and each time the question about light transmission in 1" vs 30mm has been asked, and each time the answer has been "no difference".