They're close mechanicly, but not identical. I have both and prefer the .22/45 for all the reasons stated so far. That plus the trigger is better, in part I believe because the guts of the trigger rub against polymer instead of steel. It just seems smoother to me.
One .22/45 I have has run through somewhere around 35K rounds in about two years of shooting. I shot it twice a week, at least, for slmost 2 straight years, took it home and filed stripped it after each session. I haven't noticed any looseness of reciever to frame fit, or any wear of the polymer lug that holds the reciever in place. I figure that all that shooting is about what a typical plinker is going to see in a typical lifetime, so I wouldn't be too concerned about wear.