It's time for a rcamuglia/Formidilosus unknown distance shootout! Kidding...
So - if there's an 18" (horns not body) antelope at an unknown range, but out like 600-700 meters, no LRF handy. A guy is better off mils, moa, FFP, or SFP?
None of it matters. In that situation you're going to miss. A lot.
Both MOA and mils work. Just that people pick up how to run it with mils faster and easier. Probably because they aren't trying to constantly equate everything to inches.
Both work. Both are effective, one is just about 50 times more common and has the benefit of being broken down into tenths which our brain prefers.
