Stump, the 30mm refers to the tube diameter of the Nikon not objective. The zeiss has the standard 1" tube like most NA models. He is looking at the 44mm in Zeiss and 50mm in the other manufacturers for objective size. In which the conquest with a 44mm has 3.5" of fixed eye relief, nikon has 4" and the loopy is variable dependant on the power setting. All the scopes listed come with lifetime warranty, in fact I think most do now a days. The real difference with the warranty is if a problem arised how is that handled!
You don't have to worry about swaying me with your response that is the kind of thing I was looking for to pass on to him, ultimately it will be his choice not mine.

Thanks again