I'm very invested in a particular niche game for a niche hobby (Dropzone and Dropfleet Commander (tabletop wargaming)).
About 2 years or so ago, the purveryor of the game changed hands from one company to another... (though the creator of the game stayed on board).
This switch over coincided from a stance of "We have a forum, but barely moderate it and we barely engage with social media" to "We don't support or want a forum. We engage through facebook. We promise X amount of updates/etc."
With X being about 30% more than what has actually been given... which considering over-promising is an epidemic... I don't think is too bad.
As this occurred there was must hand wringing by the forum-people... and I decided that I would keep up with both. Ultimately though, the community in the forum died off, whilst the community in Facebook has grown or otherwise stayed the same.
In this particular niche group... neither group was more or less negative than the other. The big difference in content though, was images. People could easily post images to facebook whilst they could not in that particular forum and required the tedious process from camera to 3rd party to forum.
So I think in some ways, the nature of the group matters... in a group about painting tiny tanks and such... showing off those tanks and such is the prime activity... if it is easier on one platform vs another... than that is the advantage.
GC however, is a digital game... and ultimately showing off our spaceship designs is probably not the prime activity... debating features is. If showing off ships were... well this forum is well equipped for it (now) but the Steam sharing platform takes precedence. Debate of bugs/strategy/features is something where having a searchable and maintainable record is important...
So a forum makes more sense.
What would really be interesting though, is whether the feedback via forums vs social media differs overall and which user group spends more money on the games. I'd wager the forum goers are generally going to be more "hardcore" and their feedback more in-depth. Whereas social media will give you a greater view-in on your new/potential player base, and their complaints will better represent what your game is doing wrong to keep players invested.
So I guess what I'm saying is... the medium is affected by the nature of the topic and I think a company ought to maintain all of these. Even if you maintain a forum and clearly state "We don't moderate or discuss anything here. Good luck." that still shepherds the forum-style discussion to one place for future analysis without any accountability or responsibility.