make_shared is more performant than separately calling new and creating a shared_ptr because make_shared allocates space for the reference count and weak count in the same memory block as the client object instance (effectively giving the shared_ptr most of the performance benefits of an intrusive_ptr).
enable_shared_from_this gives a shared pointer without having a reference to any shared pointer. Therefore things like the reference and weak count have to be somehow accessible from inside the client object. Therefore, it would be sensible for enable_shared_from_this to cause an intrusive count similar to make_shared.
However, I have no idea how something like that might be implemented (and I'm not sure I'd follow what was going on in there even if I look at the actual source).
Would it make sense then (for performance reasons) to tag my class with enable_shared_from_this if I know it's only ever going to be used as a shared_ptr and never as a raw object?