Wings3d vs ManifoldLab

[micheus]

I waited for an answer from dgud and as that never happened I forgot to answer something about it. I can only spell for what I have noticed along the years this kind of subject comes around.

My question is 'Are these two so variant that the merge will never happen into one monogamous tool?'

I don't think this will happen someday. All this years ggaliens never made a pull request from his ML pack to dgud's repository. And doing that, it would not be garantie of its inclusion in the main code. dgud is very rigid about the stuff being added to the main repository, its consistence and readability - since someday someone else may need to maintain it.
Dependence of 3rd part software as the CGS one use by ML is something that uses to be avoid in the main project.

My concern is at some point will my other choice files diverge from a standard Modus operandi? As in an incompatibility chasm leaving me hanging onto the edges of each usage pattern in my development?

The file content has not changed for years. We still can open projects created for v1.0. So, since ggaliens tools is producing Wings3D content you probably will not have any problem of that kind.
The latest version of ML available (2018-01-15, stated as v2.0.0) is based on the old UI (v1.5.4). So, the only issue you may to experience is related to the Preferences files storing different informations related to the UI layout.

I use both MFL and Wings3d. MFL for the boolean plugin and Wings3d to stay in touch with the non forked.

If you really uses ML for boolean operations, maybe you would like to check if the native Boolean (*TEST) option is working for the most your cases (it doesn't handle coplanar faces. But, it's something we sometimes can handle).