I have tried both Freefind and Google. Freefind is excellent for the amount of customisation it allows you and scheduling of how often you want your site indexed. Google is only any good if they have already indexed all your pages, but doesn't match Freefind in its abilities.
I've not tried Pico on a site myself but I have used it on other sites and I find it is often slow and not as good as the previous two.
You only have one chance in life - take it while you can