I think #SimpleX chat is more private/anonymous than deltachat bc simplex profiles can have one time invites whereas deltachat profiles have static invites until you delete the profile: meaning anywhere you send that invite to can be corroborated with anywhere else you share the invite either by a compromised contact or the contact themselves.
Another problem with static invites is they can be shared without your consent leading to invite flood harassment, simplex has optional static invites for profiles if you need them but they can be rotated without losing your contacts and you can use static and one time invites at the same time
Also simplex has quantum resistant encryption deltachat doesn't. Quantum is a problem now bc of the store now decrypt later attack
Also simplex supports tor integration in the app allowing you to connect to a tor proxy i dont think deltachat does that
Simplex of course has a lot of the same advantages as #deltachat open source end to end encryption, decentralised relay server model, no account passwords (client side passwords optional)