The fee on member payments is the number that matters
Subscription price is the small number. A platform taking 8% of a $4,000 monthly membership costs $320 a month on top of its plan fee — more than any subscription here. Fees range from 0% on higher tiers to 12% on entry plans, and the tier that removes them almost always pays for itself before you expect. Calculate total cost at your realistic revenue, not the plan price.
Notifications decide whether a community survives
The single largest predictor of engagement in our pilot was not features but whether members were reliably pulled back. Email digests, mobile push and sensible defaults matter more than any gamification layer. A platform whose notifications are weak produces a community that quietly dies regardless of how good the interface looks.
Decide whether you need public or private
Discourse is built for public, searchable, SEO-visible discussion — valuable if the community is also a support and acquisition channel. Circle, Skool and Mighty Networks are private-first, which suits paid membership and is invisible to search engines. This is an architectural choice rather than a preference, and switching later means starting the archive again.
Migration is close to impossible, so choose carefully
Community data — posts, threads, member history, active subscriptions — is the least portable content in this directory. Discourse is the exception because you can self-host and own the database. Everywhere else, moving means asking members to re-register and losing the archive that made the community valuable. Weigh that before committing.