FWIW-- my main range gun is a 6'' 686, with the lock. It is approaching 5000 rounds through it, and I've not had an ounce of trouble with the thing.
Regarding lock-up and the 'quality': I can say this- I also own three other SW revolvers, ranging from 1962 through the late 80's (model 29, 36, and 17), and the lock-up is as tight on my 686 today as it was when I bought it, as well as tight as the other revolvers I have from an earlier Smith era.
Regarding the "Clinton Lock" as others have put it: this has never been an issue, nor have the MIM parts. One thing you'll notice on a Ruger is the warning label about reading the owner's manual stamped on the barrel. I find this more obnoxious than the hole, personally. It really irritates me when people overlook one lawyer's mark for another, when the functionality of the lock has been, for me, a complete non-issue.
Two additional pros for the 686: the trigger is single action is absolutely stellar out of the box, and the gun also shoots lead bullets well. I've shot lead hard cast from more than one Ruger whose barrel/bullet fit were not just right, and one had a decent size burr in the rifling that lapping the barrel would have taken care of. I've pushed hard cast lead in 357 mag upwards of 1400fps without issue.
In the end, they're both fine guns, I just wanted to provide some positive feedback for the newer Smiths. I'm not sure they were any cheaper, dollar for dollar, in the 80's, 70's, etc.