S&W!
Just my perspective so don't get your panties in a bunch of you don't agree.
So I own a Ruger (Blackhawk 357/9mm Convertable) and it is a fine revolver but if you are going to shoot your revolver a lot a S&W is a finer revolver. Everyone talks about how strong Rugers are
(and I don't dispute that) but when you look at what the top revolver shooters in the world are shooting it is almost always a S&W. If you going to hot rod cartridges and just shoot a few of those fireballs till you can't think right a Ruger is a fine choice but if your going to shoot high volume think S&W
The USPSA Revolver Nationals, since 2013 is a stand alone match. The match attracts the best revolver shoots from all over. The match frequently has 100+ shooter in attendance (except this year, 86) and yet you can count the number of Ruger shooters in attendance on one hand. Two hands would cover 2013 to 2016 added together. These guys are shooting their body weight in bullets or more through there revolver each season and they almost always select a S&W. Now we can argue USPSA rules catered to S&W since they allow the 7 & 8 shot revolver to play and even before that rule change the rules heavily favor the 45 ACP revolver.
So IDPA is far more friendly to Rugers product line. The Ruger Match Champion was made for IDPA rules (or was that the other way around). So even with a rule system much more friendly to Ruger's revolver products the IDPA nationals the last few years I can find data for is still 80+% S&W in the Revolver division(s). The best revolver shooter almost always pick S&W. No doubt a similar story could be told with ICORE.
OP I would serious give a 686+ (7-shot) a look and if you might also give a 627/327/R8 (N-frame 8-shot) a look. You say the GP100 fits your hand better. That maybe true but revolves because of the frame can accommodate a huge variety of grips shapes. There are more grip shape and material for revolver grips then you can imagine. I would not shy away from the S&W just because of the grip. A grip can be bought or made that will make your hands happy on almost any revolver out there.
A rambling S&W lover...