APC is 5 times faster than Memcached

http://stackoverflow.com/questions/1794342/memcache-vs-apc-for-a-single-server-site-data-caching

Google say that APC is 5 times faster than Memcached, my experience say that APC is nearly 7-8 times faster than Memcached.. but, memcanched can be accessed by different services (for example, if you run mainly on apache and delegates some traffic, e.g. static contents like images or pure html, to another web-service, like lighttpd), that can be really usefull, if not indispensable. APC have less feature than memcached and is easly to use and optimize, but this depends on your needs.

If (and only if) you have a web application which has to live on different webservers (loadbalancing), you have to use memcache for distributed caching. If not, just stick to APC and its cache