Both are necessary. Neither is superior. They are complements.
I'd hived the idea from elsewhere, and this piece discusses it in the context of trying to form a new community (largely failed), but the ideas may interest:
https://old.reddit.com/r/MKaTH/comments/4ntf5p/public_privat...
https://www.ribbonfarm.com/2010/10/27/warrens-plazas-and-the...
The Evaporative Cooling Effect is also a useful notion.
http://blog.bumblebeelabs.com/social-software-sundays-2-the-...
Archive as site seems down: https://web.archive.org/web/20101012105003/http://blog.bumbl...
Salons in 18th and 19th century Europe generally revolved around one or a few wealthy patrons of the salon who not only funded its operations but also attracted the luminaries and intellectuals to its doors.
The analogue of patrons on the internet would be forum moderators, website owners, group creators, etc. But only to a certain extent because the owners and maintainers of an online forum are far less personally engaged with the conversation and daily goings on.
Of course the scale is much larger on the internet, and we don't actually deal with one another face to face. Banter is usually restricted as well and discussions are highly focused, in contrast to salons which were more of a social club.
[1] https://conversational-leadership.net/coffee-houses/https://...
[2] https://sites.google.com/a/wisc.edu/ils202fall11/home/studen...
I think the whole relevance of the "coffee house" in the Enlightenment was that it was a space where different people were talking to each other and sharing ideas.
Does that happen in coffee shops anymore? Do strangers talk about more than pleasantries, if that?
Even in Vienna, which is somewhat of a self proclaimed coffee house capital of the world you can't really have any prolong conversations with strangers to exchange ideas. Beer houses of today are probably more suitable for discussions.
The public square serves a vital purpose in public discourse and society at large, but it isn't actually where great ideas are born; it's where they're tested. Traditionally, salons and small groups are where great ideas are born and polished before being presented to a public. Otherwise, you're fighting a low signal-to-noise ratio that hampers motion.