Part of it is the better UI and new tech, but there's a lot more too.

Just on that point though: there's actually another open-source platform called Trustroots. They initally started as a rewrite of the BeWelcome frontend, but because of politics and such, BW never let them merge those big changes, so they spun off. Trustroots is a cool project but I think they swung too far into the realm of anarchism in their vibe both as a platform (they are very hitchhikey, so their moderation model is extremely hands off) and as a project (they have this things called a "do-ocracy"). We think there needs to be some planning and roadmapping and a healthy mix of dev + non-dev, as well as serious moderation to keep the platform safe.