On a set power, the drop retical MOA's are determined by a set ballistics profile and corresponding to 100's of yards. For example, if you predetermine a ballistics profile with atmospheric conditions of 55 deg, 1000 ft elevation with a G1 BC of .5 with muzzle velocity of 2800fps the drop reticals on a set power will be corresponding to ranges of 100 yards, 200 yards, 300 yards and so on.
Lets say your rifle after a hundred rounds or so changes the way it likes the current ammunition you are shooting and you need to make a change. Your new ballistics profile now may no longer match the 100s for drop. Your old 400 yards may now actually be 440 yards or 370 yards and so on.
Drop reticals work great if your ballistics profile does not change. What if it does? Where is the flexibility? Straight MOA reticals provide this flexibility by use of drop charts and a little help with memorization. With a little practice drop charts can be just as quick.
I would ask myself this, do I think I may need to change ballistics profiles on this gun. Would I ever purchase another gun and potentially using this scope?
If I had to guess I would say 9 out of 10 LONG RANGE scopes sold have MOA vs drop reticals.