Using as a library of managing membership, Is serf just provides a different/better implementation of memberlist?

https://github.com/hashicorp/memberlist/issues/46#issuecomment-127439840

I found some comments here quite useful, but wanted to know more about the difference/decisions about the two projects:

AFAIK:
* memberlist is a library for managing cluster membership. It implements the gossip protocol.
* serf depends on memberlist. Even the serf.Config depends on memberlist.Config

serf seems provides more functionalities but if I just use as managing membership, what are the key difference in the implementation?

Or a big part of my question is -- why does serf depend on memberlist?