We took our tandem on a nice tour of Sonoma County a couple of weeks ago that included the second half of the Terrible Two course. If those are the kind of Sonoma roads you plan to regularly ride (i.e. steep, prolonged descents with bad pavement and multiple off-camber hairpin turns), you will probably want a full on drum brake unless you are a very light team or very confident descenders (or both). I am not known for being particularly timid on descents, but I have to admit that in some places (like the descent from the summit of Ft. Ross to Cazadero) I was on our rear disc brake so much and so hard that I was worrying about melting the knobs off --- something which other posters to this forum have apparently accomplished. To our delight, we found that our disc brake passed this harsh test very well --- but we were definitely riding the brakes in places and a drum would have been more appropriate.

It's nice to know our current brakes will get us down that kind of hill when necessary, but if we were doing that on a regular basis I think we'd definitely be considering a drum.