[nchuhoai]

How would Mutations compare with Concerns, which seems to be DHH's preferred method?

[bemurphy]

One big difference would be encapsulation.

With mixins (sometimes called Concerns), you have a shared state between the module and the class including it.

With a real class, you have your own space and (probably) don't have to deal with state and method collisions.

Pros/cons to each surely, and a lot is a matter of taste at that.

[jbverschoor]

I don't see the correlation here