I like the MIL/MIL personally. Alot easier doing calculations for me in my head. MOA is better if you want to make finer adjustments since 1/4 MOA @100 is 1/4" versus a tenth of a mil is .3 inches.
Just my opinion though!
Subtensions I like thinner for shooting for groups and a thicker line for hunting!
I like using MIL/MIL for reasons already stated. I have no problems with scopes that are MIL/MOA... I have and regularly use MIL/MIL and MIL/MOA back and forth... causes no issues for me.