Originally Posted by
BBnet3000
for road bikes and tandems it might be better the other way around though, because with higher pressure tires the rear rim brake can built up heat and thus pressure in the tire, and for tandems because with the heavier weight you will go through rear pads like hell if you are using it on hills all the time.
Good point, tandems, tourers and utility bikes behave different as the rear axle is directly loaded. So that rear brake will actually be useful on downhills. So ... discs on both are ideal.
For the typical non-cargo single occupant scenario, front disc only is all that's ideal. I would recommend anyone who upgrades to go with this scenario as it is the cheapest, lightest and does not compromise any rear wheel weight with a reduced dish.