I have a basic 686 6 shot that's very accurate. My final zeroing group when I mounted an optic was 5 shots just under 1.25" at 25 yards using handloads with once-fired brass. I suspect that a better benchrest shooter than me could get closer to an even 1.0".
I'm not going to say that all 686s are this good, but S&W is certainly capable of putting out 686s with excellent accuracy. A friend of mine who's a better shooter than I am (he's got some very nice S&Ws of his own) stacked round after round in a ~4" oval at 25 yards shooting unsupported with PMC Bronze .38 Special. Afterwards, he said something along the lines of, 'They definitely made you a good one!'
You might find it easier to take advantage of the inherent mechanical accuracy with a Performance Center "tuned action," but accuracy variances may be more about individual guns and ammunition types than PC vs non-PC models.
As far as durability is concerned, metallurgy is very consistent these days. Even the modern K-frames with the beefed up forcing cone hold up quite well to steady .357 Magnum usage. In theory, if you're doing a lot of rapid double action shooting, the 1 oz lighter cylinder of the 686 Plus vs the regular 686 will put less stress on the cylinder stop. The 7th round doesn't give back all the weight; a 158gr .357 cartridge is just under a half oz. The unfluted Performance Center model gets some of this cylinder weight back, but I don't know how much.
