For me it was fit, pointability, and compactness. I really love SIG products, but the USP in .40 with the LEM points and fits my hand better than the 239 (and almost as well as the 220--ideally I'd carry this but it's a bit bulky for everyday CCW IWB under a loose "T" for me). USP .40 compact was a good combination of firepower, totability, and shootability. Yes it is plastic and the trigger takes some getting used to because it stages fairly sharply but it does make an excellent carry gun.
In any compromise between good and evil, it is only evil that can profit -- John Galt