www.thesession.org loads fast thanks to having almost no graphics. It doesn't need them. The forum could be more flexible but basically it works. The tune archive is very badly designed and I never use it.

www.footstompin.com has some godawful bugs which have never been fixed despite the admins knowing about them for years. It's not as fast as thesession but reasonable considering its design goals (promoting a commercial enterprise). Unfortunately the coding bugs and their attitude to them are so bad there's no way in hell I'd ever trust their site with my card details, which makes it rather an own-goal as a marketing tool.

Mudcat, on this browser, is the clunkiest of all, frequently loading too slowly to use or locking my whole machine up. Unless I disable Javascript, in which case it's the zippiest and most reliable web forum I've ever used. Disabling Javascript also means I see almost no adverts. Own-goal in a different way.