G'day tentman, it sounds to me like you are talking about eye relief and parra lax.

The Leupolds are trim and light and some, mainly lower magnifications( 2.8-8), have good eye relief. Eye relief is the distance behind the scope your eye has to be to belooking throught the scope and see the whole picture not as if looking down a pipe. Eye relief can be from say, just picking figures to demonstrate- 90mm to 95 mm from the ocular lense or 90mm to 105mm.

The Euro scopes generaly give you better clarity, can use them longer as the light dims at dusk etc, but hve bigger ocular lenses, they also have fast fiocus for the eye piece where as Leupy's it is a case of set it and lock it in.

Cheers