As far as the history of Map-Editors and what the latest and greatest should be...I'd go for the H5 Editor but seriously refined and made every bit as detailed and user-friendly as H3's. I didn't mind the learning curve for the H5 editor but what I did detest was that it was introduced to the public is an in-house, as-is shape and very bare of the basic "must-haves" to help people create a map.
<imo> If instead of the H6 fiasco they'd just went it and gave the 3d editor all the one-click features and replaced all "forced" scripting to do the simpliest actions of the H3 Editor (like objectives)than I think results would have been far better.
However, as Sal said, as well as others, if the game does not run well? or is of ill-design? etc. then an awesome-Editor, whether for map or campaign...will serve no purpose in the end. We have to have the Horse first or the cart will sit unused. <L>