I used to own a Chapuis, I've shot several Merkels, and I've handled several Heyms and Kreighoffs. Much of this comes down to personal preferences and also the quality of individual gun. I've seen a wide variety of quality variance in Chapuis and Merkel rifles. Heym's I've seen were of more consistent quality and are supposed to have higher standards in terms of regulation. I was not entirely happy with my personal experience with Chapuis, but I've seen and shot other people's Chapuis that were of a more consistent quality than the one I bought.

Its good to keep in mind these are "factory/production" made guns there are not Purdeys etc. so its good to have realistic expectations.