Redundancy and percentages aside, the biggest problem you will have with front-brakes-only is when you have to brake over a turn. Once the front wheel locks-up over even the slightest patch of sand, gravel, snow, you're screwed. The front of your bike will skid and you lose all steering control. Good luck trying to keep upright and in one piece.
The right way to handle a bike in that situation is to let off the front brake just enough to get the front wheel turning (and steering) while at the same time using your rear brake to slow/stop. If you lock-up the rear and things are looking grim, its much safer to bail on a rear wheel slide than a front wheel slide.
That is also the biggest reason I don't like dual-pull brakes, because you lose the ability to modulate front and rear braking power during emergency situations.
