I can only speak for Seba, who started to built a bipe just for comparison, and ended up to discover that his bipe flies better than the monoplane for his kind of flying style.
In general terms, Seba discovered that his bipe flies with a more constant speed troughout the flight envelope, and is less "challenging" during all the manouvers the require high lift in knife edge attitude.
It is also less disturbed into the wind.

The prices to pay are:
Higher weight.
Huge amount of complexity in setting up the airframe ready to fly.
More care on the airframe needed.
The model is more prone to have failures, because of his complexity. (Murphy's law..)