I have a P223 3-9 and a M223 4-12. Shooting them back to back I don't notice an real difference in the glass of the two, at least in daylight at the range.
I mention this because I have a couple of M308 4-16 and think they have very good glass. If the comparison between the P and M 223 holds, I think that would be an excellent scope at that price point.