I never really kept track of which end gets more wear faster, I know the one I've been shooting the last several years is looser than when it was new after approx. 4000 rounds or so. It's still as tight as a brand new series 70 Colt I bought new in the box a long while back. I don't like em too tight myself, just want it to lock up nice when in battery. I figure things have to wear eventually?
The flaw really shows up more when we go to the stronger recoil spring.
Might I ask why a stronger recoil spring is used in the first place? I never used anything stronger than a 16# in any of mine, and they seem to be a bit much till they get broke in some. What comes back, has to go forward, there is a wear factor on slamming the slide home as well. I was able to slow down the rearward movement of the slide a wee bit with a very thick firing pin stop with almost no radius, just the edge broke and smoothed, I think I prefer that way instead of a heavy recoil spring myself. FPS change was real noticable while shooting and working the slide.