I dont think 30mm tube passes more light than 1inch in any scope. The thing that affects amount of light passed is objective size. If one compares the 44mm version of Z5 against the 44mm version of VX5HD or VX6HD, the light passed should be the same.
Glass and coating makes a very small amount of difference to amount of light passed (they make a far bigger difference to colour accuracy, resolution and contrast) but generally speaking human eyes cannot detect that difference. From memory anything under 1/6 EV (about 17%) difference is not detectable.
The Leupolds offers a lot more adjustment range than the Z5. Both VX5HD and VX6HD offers 75 MOA elevation, while the Z5 offers 58 MOA. That is due to the tube size difference.
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