Since I've not shot one or owed one my remarks are pretty limited to the 5-7 or so I've held, looked at, etc.

Now we can all quible over asthetiques and such, but I'm not going to talk about that since that's a matter of taste. I'd say the quality of the Heym really is on another level than Chapuis or Merkel. The level of finish, wood to metal fit, etc has been better on the Heyms I've seen in general. There are exceptions, like the "hand finished" Chapuis that you can special order are much better than the "factory finish one" (of course they cost as much as a Heym so...), but in general Heyms look much better finished. I'm not an expert so I can't get into specifics, sorry. I've also been repeatedly told that they are very well regulated, but that's all second hand info.

Sorry I can't be more help