I've had a couple 686's in the past, but ended up getting rid of them. I currently have 3 different GP-100's. I, for one, much prefer the GP over the 686. I like the looks better and I'm more comfortable with the idea of feeding them the steady diet of hot handloads that I use. The 'push-in' cylinder release is more natural for me to use quickly for speed reloads than the 'slide-forward' style that Smith uses.
The triggers aren't as bad as most would have you believe and they are quite easy to make better if you so choose - with very easy to change springs and a little polishing with a buffing wheel on a dremel. I own several other S&W revolvers, including a couple Performance Center guns, and I'm here to say that I'd put the triggers in my GP's up against any of my Smith triggers.
As a shooters gun, one of the biggest reasons I like the GP's over Smiths is I really like how the Rugers are timed, where the cylinder rotates and locks well before the finish of a double-action trigger stroke - allowing for very easy, and quick, manipulation of fine trigger control for accurate shots. All of my Smiths are timed so that the cylinder locks much later in the cycle, making it (for me) more difficult to get fine control of the DA trigger stroke.
Really you cant go wrong with either one. But the truth is that as far as quality and workmanship of new specimens of either brand - there isn't a hill of beans worth of difference. I think most folks who would really try to convince you otherwise are doing so more out of brand loyalty rather than a legitimate unbiased opinion.