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.