The stopping power of the drum brakes was definitely good enough for me, once upon a time when my Strida 3.1 was new. But two years of NYC traffic later, the pads of the rear brake are quite worn out. Though the cable is nice and tight, it cannot expand the brake pads enough for them to engage against the inside of the drum. Cable adjustment is not the solution; the lever on the drum is actually bottoming out against the frame. I'm not sure how I'm going to fix this; Strida is working on a repair kit that the'll be able to send out one day, but that isn't an option right now.
I don't know what's the root cause of the problem, whether a it's an iherent flaw in drum brakes, or something about the way the Strida's brake is mounted, but evidently the folks at Strida decided disk brakes would be a worthwhile improvement.
And I, now that I'm down to one working brake, I'm not going to second guess them!