They let you view logs and all sorts of stuff.
Free malware protection for DNS. THEY make basically use of Dyndns. DynDNS also gives you real malware protection out of the box. It also has an option (registered only) to block ads/popups
Comodo dns you have to install Comodos firewall and the Pro active defense package from them that throws in the crapware asktoolbar and such? Is it free?
Norton you can use without installing Norton.
Google and OpenDns make use of the phishtank which only Helps against Phishing. Phishtank is what WOT use btw.
Clear Cloud also excellent but their comming to a end i think