The main reason is the knife edge performance, the biplanes have an advantage over most if not all monoplanes (canalizer or not).
For guys flying the FAI F sequence, and unknowns the biplanes make many elements of those sequences a bit less work to fly.
That said, they make a lot of simple maneuvers like flying in a straight line harder due to the fact they just go exactly where they are pointed, and if you make a rudder correction incorrectly it will really stick out
The lighter wing loading does help in certain situations but also hurts in others (turbulence).
At the end of the day, I think everyone flies best what they are most comfortable with...mono or bipe. In order to figure that out you just have to buy both and fly them a lot
. At least thats what I tell my wife lol.
Chad