Im doing research on which one of these to use and I can\'t really find one that stands out. Eaccelerator is faster than APC, but APC is better maintained. Xcache is faster
It may be important to point out the current stable, unstable and dev versions of each (including date):
http://pecl.php.net/package/apc
dev dev 2013-09-12
3.1.14 beta 2013-01-02
3.1.9 stable 2011-05-14
http://xcache.lighttpd.net/
dev/3.2 dev 2013-12-13
dev/3.1 dev 2013-11-05
3.1.0 stable 2013-10-10
3.0.4 stable 2013-10-10
https://github.com/eaccelerator/eaccelerator
dev dev 2012-08-16
0.9.6-rc1 unstable 2010-01-26
0.9.5.1 stable 2007-05-16