Essentially they are both the same thing, angular measurements, and can be used to do the same things. So it is mostly a matter of choosing which one makes the most sense for you.
I encourage guys to not get too caught up in the math because if you are using the reticle correctly there is almost no math to worry about, unless you are actually going to use the reticle for ranging. But if you are using the reticle for holdovers, windage, to call hits and misses, etc. there shouldn't be any math involved. If you are going to use the reticle for ranging then usually the math for one of them will make more sense or be more intuitive.
What ever you do get your reticle and turrets to match. Both of the scopes you are looking at do this so you should be good to go there.
MOA is a finer measurement than MIL so each click on a MOA turret will move your reticle about .26 of an inch. With MIL it will move it about .36 of an inch. I personally like MIL's because i like dealing with smaller numbers which is easier to remember and is also faster to turn on the turret. A 1/2 MIL hash reticle is just about the right combination of precision while not being too cluttered for my eyes. If you are shooting really long distance, over 1200 yards then the finer adjustments that MOA provides may be an advantage as long as your scope allows for enough adjustment.
HTH,
Scot E.