I guess it really depends on your requirements ... its easy to say wordpress is great for a lot of things ... throw in caching and you've got something that a lot of clients are very happy with ... bung on firestats and they go ... oooh .. ahhh
add in the
seo modules and away you go ...
what specifically about joomla are you using ... I'm aware there are loads of modules .. but given its at 1.5 and a lot of the modules no longer work with it ... without hacking ... what in particular do you like about it ?