Why would they be harder?

I favor Biplanes over monoplanes.

I had NO problems switching over from my first plane (a tail dragger PTS P-51D) to a 40S bi-plane.

This is a small sized 43" biplane, as a result it is comparatibly "twitchy", in that it responds to controls very quickly, but a rather small amount of Expo fixed this minor problem.

My larger Bipes, such as a Skybolt, has no such idiosyncracy.

If anything I find BiPlanes a lot of fun to fly.

They have more lift and drag over monoplanes, so they have no problems with all sorts of stunts.

Even my 40S (World Models Ultimate 40S and Nitro Planes 40S) snap roll like demons. So fast you practically cannot see it.