VS the 5.7mm, i'd rather have 7.62x25. BUT the idea of having a STD 20 round magazine and a extended magazine of 30! rounds. That's nice. Now we just need to do something about fast follow up shots. If I were limied to small capacity, i'd definitely want somethings like a.40 or .45. As it is the 9mm is about the minimum with the limited California magazine clause.
Good luck
-bix
