There are single-pivot sidepulls that rock, and single-pivot sidepulls that suck. There are traditional cantis that suck, and traditional cantis that rock. What Retro Grouch said - it's impossible to generalize, here.
Clearance is an issue I didn't think of when mounting cantis on a new frame. The yoke that came with the Tektro Oryx brake arms just didn't get the job done; I attached Dia-compe straddle hangers and cables instead. Whoops. Brankes work but now it's going to be a tight squeeze to fit a rear rack without distrubing the cables.