The E-Flite UMX Pitts and PT-17 fly unbelievably well for being both small and biplanes. These glide almost as well as many other small single wing foamies too. A biplane should fly as well as a monoplane with power, but as Daveopam notes above, they generally won't glide very well. The other issue some have with biplanes is the CG. It is far forward on some, which means adding more weight to properly balance

Bill Kalb in Pegasus RC in Hagerstown, MD only flies triplanes. They all fly great, but difficult to land without flipping. Bill makes it look easy....