A 640.

As I suggested in your other thread, what I do is have 2 - 642’s and 2 - 640’s, use the 640’s for most of the range time and belt carry, the 642’s with just enough range time to be comfortable with them and they are my pocket carry.

I’d compare the 66 to a 640, as the difference is significant (at least for me), but then my Md 66 2.5”ers are pre-lock, so my comparison may not be equal to the new “post lock” ones.

At least that is what works for me.