Double ratchet is simple to implement and works well for 1-on-1 chats. MLS is better for groups. In case the MLS is also good for 1-on-1, happy to change.
Discussion
From my understanding, it is equally good for 1-on-1 chats
mls for 1-on-1 chats is basically signal with a negligible overhead (it becomes the same thing in practical implementations in a multiple-nodes network).
Very soon, I'll be able to share some stuff with you on the MLS stuff. Would love your feedback (and review) of things when I get there.