As stated above these are all just different ways of measuring an angle.

MIL has become popular due to the military use of the measurement. Stems from artillery where they used mil angle to adjust the elevation and azimuth of the gun. The spotters gave adjustments in mils so all the military binoculars and scope sights were marked in mils.

If have a scope marked in mils then just ask the spotter to adjust in mils. Same for MOA.

Just don't get a scope with turret adjustments in mil and reticle in MOA. It gets confusing. :)

I like MOA for shooting rifle just because most targets are marked in MOA or inches and it is a familar measurement for me. And, yes, I used mils for almost 20 years in the Army. Then I started 'shooting' lasers and we used micro-radians :)