If you work with the metric system more, use Mill. Imperial more, use MOA. The Concept is the same, just takes some number memorization and you can switch between the two pretty easy.
If you don't understand the difference between FFP and SFP, you probably don't need the extra cost of FFP. My advice is to understand MRAD or MOA completely before buying anything, then make your choice of scope. It will help with reticule selection.