_you_ don't get managed hosting from mastodon.social the site owner does (if they used a service like this). You just get an account that someone else manages the infrastructure beneath.
This gives you your own instance, which in addition to using your own domain, means you can can set the rules of the server (what kind of speech is and isn't allowed), you can boot people you don't want. You can control who gets in. you can control what other servers are blocked (i assume that is an option in pleroma too).
Do you really get to set all the rules? This lists no terms of service at this point, but is there any reason to assume that the rules will be significantly more lax than e.g. twitter.com?
As a person who've had their VPS disconnected by OVH over a malicious link posted by a third-party on my service, I am very skeptical.
Additionally other instances could very well block all Togethr instances if they see abuse from customers, the same way they can block an instance if they see abuse from their members.
This gives you your own instance, which in addition to using your own domain, means you can can set the rules of the server (what kind of speech is and isn't allowed), you can boot people you don't want. You can control who gets in. you can control what other servers are blocked (i assume that is an option in pleroma too).