memcached is multithreaded, so it scales up better per node.

memcached clients also frequently uses ketama consistent hashing, so it is much easier to do load/clustering, being much simpler than redis clustering (sentinel, etc).

Mcrouter[1] is also great for scaling memcached.

dragonfly, garnet, and pogocache are other alternatives too.

[1]: https://github.com/facebook/mcrouter