My opinion: Avid's mechanical disc offerings, as well as Shimano's, Hayes', etc will all offer pretty good, functional braking, if set up right. If you want really good, and I mean REALLY good, disc brake performance with drop bar levers, you can't get it cheaply, and even then, it's an iffy area at the moment. The road/CX market's just not there yet. Affordable, high quality and trouble-free hydraulic systems will be the eventual answer, just like it has been with mountain bikes.

Again, just an opinion.