-- "... much more secure ActivityPub."
Security between #OStatus and #ActivityPub is exactly the same. If that's the sole advantage you're looking for, you'll be soundly disappointed on an AP-only network.
As for the #blockwars problem that Roy @schestowitz mentioned, the only possible solutions are (1) to put better blocking and filtering tools in the hands of the users instead of concentrating more power into admins' hands; and (2) smaller instances instead of larger ones.