You want to start new discussions regularly. If you decide to host a chat space, you might prefer one of the free community spaces listed above, since they provide a large pool of chatters to choose from. You want to develop a line of thought over days or weeks. You want past discussions to remain available for new participants. You have an idea-based community.
Discussion spaces work well on any of the software mentioned above.
Our only caveat is to be certain that the software and server are reliable, because discussions suffer from interruptions. Linear flows in a straight line. Someone creates a topic and all of the responses within that topic are added below that opening message in the chronological order. The Well uses this kind of linear software. Threaded software branches out from an initiating message.