To add to it (and absolutely not to say one is better than the other!! I’m not into that):
@flannelhead for example is also involved in the development of filmic, and still very active in the main DT space (And still thinking of ideas where to go to next with filmic, I believe 
).
I’ve had bugs in things like color-calibration auto-detect modes, which were fixed by DT community members.
And - at least as I see it - R&Darktable at the moment has no features that main Darktable does not have, main Darktable has (major) new stuff that is not in R&Darktable.
R&Darktable doesn’t seem to have work done to it (on github at least) since august, and those changes were cleanup changes and ripping stuff out changes.
So… I don’t know if the people still around DT know the insides of AP modules as good as AP. But they do know them. And there are developments. So those modules will not be deprecated or left out to die anything soon.
I used r&Darktable when it was new, and it had some tweaks that i liked to defaults … But i quickly went back to DT the moment huge developments arrived in DT that were too awesome to leave behind.
I love AP for what he has done , and i can handle his language and ego so to say. But i have the feeling that DT has received a place where he is quite happy with it, so it gets less time from him.
Maybe if he comes up with another awesome idea and new module , AND doesn’t want to help DT integrate it, there are still people around that could port his new features to DT.
What I’m trying to say is that i don’t suspect problems with the AP code currently in DT being unsupported. And i don’t see issues in both projects existing side by side . And changes from one can be cherry picked in the other.
Time will well the truth , but at the moment in use DT is functionally not behind r&Darktable , but not the other way around. So DT is the one to be for new stuff. At the moment at least.