I started this thread back in March and I appreciate all of the informed responses thus far. IMO, there are no real downsides to adjustables over fixed sights other than the initial added expense but with two caveats: one, if the intended purpose of the handgun is "deep-cover" (i.e., pocket carry) where a snag-free draw is needed or, two, if the pistol is to be employed on the battlefield where extreme rigorous conditions are anticipated.
In my experience (33 years in le carrying a handgun of one type or another daily), the often heard criticism of adjustables being unduly fragile is, IMO, just folklore. In numerous "scuffles" I had where my handgun with adjustables got banged around, I experienced only one occasion when said sights were damaged. This incident occurred while rolling around on the ground with a parolee who didn't want to go back to prison and the blade was partially snapped off. I can tell you that, in that situation, if I had needed to use the gun, I wouldn't have needed sights of any kind.
On the other hand, contrary to the experience of others apparently, I have not found it unusual for me to have a handgun with fixed sights point of impact to not correspond with my point of aim. That situation, of course ,requires either knocking the rear sight one way or the other, removing some metal from the front sight or, in extreme cases, turning the barrel (of a revolver) one way or the other (I'm not an advocate of "Kentucky" windage). And, after doing the adjustments to the fixed sights, your load selection becomes pretty well "fixed" too.
Because I like to reload as well as experiment with various factory loads and to try various bullet weights at varying distances, most of my handguns will always wear good adjustables (exceptions, of course, being my Smith 642 snubbie-used for pocket carry, and my Ruger Vaquero- used for "cowboy action" shooting). All of which is why I inquired about having a set of quality adjustables installed on my 85B. I will be following up on some of the good suggestions offered. Thanks again.