I'm willing to concede that the problem I'm feeling in my friends ILS-equipped 686+ is due -more- to the presence of the lock (or the drop of quality/finishing of newer revolvers) than it is due to the fact that it's a 7-shot cylinder rather than a 6-shot cylinder.
However, if you take the same exact cylinder size and instead add another ratchet so that it's indexing a bit shorter and locking a bit earlier than what you've previously been shooting for a quarter century -- I won't accept any argument that tells me "it's the same, just has one more shot." It is -not- the same.
I bought my 686-3 brand-spanking-new, shipped to my kitchen table FFL from his wholesaler in 1989 and I paid for it with saved up paper route money. This may have been a number of years ago, but man, it did -NOT- have that dead-stop hitch, crunch, and pull-through-to-discharge that my friends (also new) revolver arrived with. It was purchased new, from Bud's in Kentucky.
The newest (to me) S&W I own is a 19-3 and I first came across this revolver four years ago and it was offered as having been unfired and all the evidence with it backed it up. Even if someone had taken 6 shots from it, the point was the same -- it wasn't the difference between "meh, ya shot that one a thousand times and this other one is new" This 1974-built 19-3 had not been run, maybe ever, and the double action on this revolver is what you expect from a Smith & Wesson. My pal's 686+? Sucks. But it's not mine. If it were, it'd be headed to the east coast.