After I posted that reply, I suddenly became very confident it had to do with coloration/genetics/etc, but I figured not to edit my response to try and cover my lack of knowledge, haha. But, hey...E for Effort? Eh? No? ...well, I did my best.

Anyway, yes, yours are definitely VERY clean-looking. I must say, I'm experiencing some envy over here. (but, not the resentful/mean kind, the positive kind, if that makes sense.) I'd have a tough time choosing which to keep, too!