If the S&B 3-20X50 had been available at the time the USMC contracted the S&B 3-12X50 day scope do you think they would have chosen the 3-20X50 instead?
I would wager size of the scope and the fact they are killing people with it vs. a paper target had alot to do with their choice. The 3-12 is more compact. They don't need the magnification as much as LE might.