For the average user does it even matter what server/instance you join? From what I can tell, once you sign up you can search for, follow, find, post, re-post etc. anything from anyone regardless of which server you sign up with.
This is the wrong question to ask. Last I used Twitter it bombarded me with unsolicited, unrelated content to an inescapable degree. On Mastodon, which so enthusiastically compensates for Twitter’s aggression that no new content is surfaced without an explicit request or first-degree vouch, I take a peek at instances' local timelines almost daily.
Beyond the timeline, consider the behavior of hashtags. On a single-user instance hashtags are useless for discovery.