I like PC-Cillin, but up until version 2005, it has not shown strong
heuristic capability. Version 2005 supposedly has improved heuristics,
but I have not seen any test evidence with that version that would
confirm that.
PCC is essentially a very good pattern scanner. If the pattern files are
kept up to date, it is very efficient at detecting and cleaning up
malware problems. It's also very resource friendly.
I would not recommend switching from KAV if you're happy with it. If
not, then PCC Internet Security 2005 is worth looking at
as a replacment.