I think the benefits are just related to you being an admin. E.g. you can block instances, change settings to suit yourself, that sort of thing.

But if it's just you, then for example the "local" feed is a bit useless. The annoying quirks when you're the first person to search for a community will now happen every time you search for a new community, because you're the only person.

And of course when something breaks (and it will), it will be you that has to fix it. So make sure that's fun for you!

There would be other benefits if you weren't just running it for yourself, but had a community. E.g. if you are a subreddit looking to move everyone to Lemmy, then there are advantages to setting up your own subject-specific instance rather than just making a community on an existing instance.