Klassik 2.5-10x56 vs 4-12x50?

[Gallahad]

I'm curious as to why the lower powered scope is so much larger. I believe the 12x is @14" and the 10x is @ 17". I'm assuming it has something to do with the 10x being a low light scope as it's a larger objective? Does that length also translate into better light transmission? If someone has both, which has a nicer eye box/is easier to get behind?

 

[Gallahad]

Also concerning the klassik line, does the illuminated l3 reticle cross hairs intersect, or is there a separation with a dot in center?