Here's the dealio....
What I find most favorable about V brakes is they allow you to build a dishless front wheel and a dishless, wide flanged rear wheel (if you're talking about a single speed). You can build a far lighter wheelset of equal if not greater strength than a disc setup using non-dished, non-disc rims. I've built up silly light dishless, V brake, SS wheelset that stay in true far better than my much heavier disc sets. Vs are simple, light and get the job done on a rigid SS. On a burlier FS rig ment to tear up the downhills I don't feel Vs have enough stopping power, especially in wet weather. So on my heavy duty gearie I run Avid Mechs and on my SS I run Avid Single Digit Vs. Overall I'm faster on my SS and have more fun on my SS but hey, I still like the gearie for the easy days. Regarding the discs, the Avid Mechs do work great, are very reliable and pretty darn cheap.