I think that the 4516-1, 4516-2 and 4516-3 are all equally reliable. I currently own a 4516-3 and have shot a 4516-1 extensively. No issues to report. Just great accuracy and superb reliability, shot after shot.
A fellow on my old squad had a 4516-2 and he loved it.....still does AFAIK
. He carried it till he went to the Glock 21.
The only visible differences (exterior wise) between the three are the longer tang on the 4516-2 and -3. The 4516-3 also having laser etched markings, vice the rollmarks of the other 4516 variants.
The lack of MIM parts in the 4516-1 and early production 4516-2's is also a plus. Despite the rantings of the MIM defenders on the superiority of MIM parts, the MIM mag catch on my 4516-3 snapped, like the cheap pot metal it was. S&W sent me a forged mag catch which I replaced it with.
I think any one of these 4516 versions will serve you well. If I get another, it would most likely be a 4516-1 with flash chromed hammer and trigger.......to match my early production 3913.