Best Answer - Chosen by Asker
It depends on a lot of things. First it depends on your bodyfat. You're arms can be 20" if they are mostly fat it is not impressive at all. Second it depends on your body structure like height and bone size. For instance if you are 6'0 then 14.5" arms are pretty small but if you are 5'6 and under then its respectable.
And vascularity is part genetics and part body fat. To get that arm vein you need low bodyfat probably 10% or less if you can't see it then you just don't have the genetics for it. At my leanest 9% bodyfat I had a ripped 6 pack and muscular definition but never had much vascularity. I just don't have the genetics for it.