I have both, a 2.5" prelock, and a 4" and a 3" with the IL. I can't seem to detect any difference in the quality. All are 686+s.
I paid $350 for the 2.5" some time ago, used, no box, gorgeous rosewood, after market stocks - could be early 1990s, could be 1980s. It's a dash 4 so we can always look it up to see when those were made. For no reason that matters I had a trigger job done; it was actually quite unnecessary.
The 4" I bought about 2 years ago, maybe 3, and the retail price before I got hit with a premium I didn't see coming was $850 or $900. I don't do business with that brick and mortar auction house any longer. I think I paid $725 for the 3" last year, from a Forum member. Both of these were NIB. Neither of them needs or will ever get a trigger job while I own them.
They all shoot great and the 3" graduated to replace the 2.5" as my nighttime gun. The 4" gun is my packin' pistol woods gun. But the 2.5" won't be ignored.....
My 586 no lock has a 6" barrel - my oh my is that gun ever accurate at distance!
Just for the record, I actually EDC 2" K frames but I love the utility of L frames for other purposes.