[devbro]

the good old question and the usual simple answer:
They are both quality gun. out of the box krytac is better and stays the same as long as you don't try to open it. the parts inside are customized for higher performance and it makes any upgrades annoying even for the experienced techs.

VFC is better because it is easily modded and has many compatible parts for it. With a few upgrades (Which a lot of people do) it becomes better than krytac. even a novice can do these upgrades.

if you are not use, just get VFC.