Separate out the issues...
1. Avoid sites that force their pop-up ads on you. No pop-up ads are relevant to an amdram audience. (When did you last see a pop-up ad for Lee Gels?)
2. What do you want on your site? Most amateur theatre sites are not managed intensively enough to warrant the use of interactivity. Mostly we are just providing basic introductory information about the society (including contacts and "what's on") and an archive of stuff about old shows. That does not need a fully featured service, and free web space is usually enough.
On the other hand, if your nucleus of web-site users is large enough to support an active discussion forum, or if the commercial benefits of box-office on line outweigh the total costs, then a commercial service makes sense.
3. If you need a domain name, you can buy it as a separate proposition and route to your site. The relevant question is "How do people get to my site?" There are four answers: search engines, links from elsewhere, bookmarks/favourites and typing the url into the address bar. The last is the least common, and the only one for which a memorable domain name really helps! (There is, of course, a secondary question of "Does my site have a professional image?" for which a domain name will help.)
What a long and boring post! Sorry