There are pros & cons of both the forum & chat based communities. Really, it should be determined by the kind of community you're managing and how you want your community members to interact.

Forums are great for debugging & keeping a record of information. If your community works together on projects, chat is the way to go.

I've been curating lists of online communities at the Hive Index. For example, here's my one for programming https://thehiveindex.com/topics/software-development/. In this case, it's about 50/50 split between forum & chat. There are also community platforms experimenting with both forum & chat in the same place, for example circle.so