Everything is a compromise. A typical reason for a 50mm tube is to accomodate for low light conditions. There is no compelling reason why it can not be done with a 1" tube, like Kahles has.
I do not think anyone looking for the absolute smallest scope will be shopping for a KXi. However, it is easily one of the smaller 50mm obective scopes out there and definitely the smallest 50mm scope with an illuminated reticle that I can think of.
ILya
