SmartRecruiters vs Opencats.
There are some comments here;
http://www.opencats.org/forums/viewtopic.php?f=10&t=130
but well it depends really. The virtues of opencats are that;
a) you retain your own data
b) you can customise it yourself (career portal, joomla, drupal integration)
c) if you are a coder (or have access to a coder) you can integrate it to additional systems easily (Asterisk, CallerID, CRM etc)
That said - you will probably need to run your own instance - therefore you need to be comfortable that YOU are running a MySQL server (either on WAMP or LINUX) and that if YOU do not support / backup / maintain that server then your core business tool is dead. It's relatively easy to get a backup reigime in place - but just as easy to forget about it until it's too late.
opencats is some simple php/mysql coding (original coders of it please dont flame me for that!) and reasonably accessible to anyone looking at the code.
I suspect SmartRecruiters has more hooks in it for outlook /email integration