Good choice with the drum brakes. The only situation in which you'll get improved performance on level terrain with disc brakes is to go hydraulic. On hilly terrain, that's another story altogether, as drum brakes will fade when hot. (think long mountain descents, not just coming down a hill in the city)

Overall, assuming you use a proper 4-finger brake lever designed for cantilever brakes, and keep your brake housing as tightly bound as possible, I'm sure you'll find drum brake performance to be the equal of any caliper brake in the dry and in another league in the wet.