Security scanning recommendation?

I don't see any value in any of these services. Most consumers probably don't even know what they mean or imply, and the fact that McAfee Secure made zero impact on your metrics would seem to prove that.

In short, my vote: save your money, skip the whole idea.

Make up a clever looking icon, and have it point to a page that say "Site Protected by Tricorder Security", enter security credentials to enter, have a bogus login form, and call it good.