The best grips I've ever experienced on a revolver are as set that the late Jacques Trausch modified for me for my Ruger Security Six; they were originally for a round-butt Speed Six, and Jacques cut out the butt and heel portions to accept my square-butt frame; when I later whined about the left grip's issues with accepting speedloaders, he subsequently further modified a left grip for me. They, and the Security Six work superbly.
A fairly close second would be Ruger's Compact grips applied to my full-size 4" GP100; thankfully, these grips are now again available from Ruger at a fairly reasonable price as an aftermarket accessory.
Best, Jon