While I am not a typical precision rifle shooter, I do occasionally go out and reach to the long ranges with a good bolt gun. Like many today, I was once confused on the two major systems for scope reticles that populate the market: Milliradians and Minutes-of-Angle.

Precision Rifle Blog has an excellent write-up of the two systems and their function. They focus on the factual differences, rather than get emotionally attached to one system or another.

For those looking for the nickel-tour, the summary is below. I personally recommend that all shooters follow the last bullet point. 

• 1/4 MOA adjustments are slightly more precise than 1/10 MIL
• MIL values are slightly easier to communicate
• If you think in yards/inches the math for range estimation is easier with MOA. If you think in meters/cm the math is easier with MIL.
• If you have a friend that is already using one, there is some advantage to being on the same system.
• Around 90% of the pros use MIL
• More product options in MIL
• Whatever you decide, go with matching turret/reticle (i.e. MIL/MIL or MOA/MOA)