I’ve only heard good things about Gloomhaven.

As for KDM… I think that’s​ a much more involved game, definitely with some ingenious parts, but also such a hodge podge of mechanics and random tables that it’s very inconsistent. I expect Gloomhaven to be more straight forward and coherent, making for a less crazy experience (which can be more or less fun, depending on your taste). My group is planning to get Gloomhaven for sure.