The MK 4 is "designed" to be a dial up scope. Target turrets can be put on about any scope, but that does mean they will hold "zero" after being dialed a few times.
It is my understanding a MK 4 has much tighter tolerance internal components to ensure accuracy and repeatability of dialing the turrets.
I just bought my first MK 4 a few weeks ago for a competition .22 and so far I am quite pleased with it's performance. I have several NF NXS on my LR rifles. When you dial a 1/2 moa, you move a 1/2 moa..... period and they always return to zero. I am hoping to get the performance from the MK 4. I have tried dialing "standard" scopes, Leupold, Nikon and others and have been less than pleased. In my opinion, if you are going to "dial up" use a scope that was designed from the ground up to be used that way. Just my opinion.....
I do know this. If you go to a BR competition, you will see quite a few MK 4s but very few if any VX-3s with target turrets.