Believe it or not, I had removed Tinyboard's support of Memcached a while ago (NPFchan never added it themselves) since it was being abused for an open exploit. This has been largely patched in most installations of Memcached so I decided to add it back since you mentioned it.
I've also changed the call from Redis::delete to Redis::del to fix that deprecation issue.
As for an opinion, I'd recommend Redis more. It has a much bigger following and seems to be more reliable since I haven't heard of any deeply concerning exploits like I have with Memcached.
Also, I'd like to note ahead of time that APC will be deprecated (and eventually removed) in a future version of Tinyboard, and I highly suggest using APCu instead.