Another part of the "bigger flies better" issue is dealing with turbulence. Air is very rarely still or consistent. There are always currents and/or thermals, little swirls, and pockets of turbulence. So let's say you fly through a small horizontal swirl of air and the edge of it pushes on your wing. In a small plane, maybe 1/3 of your wing feels that push, and there is little resistance to it from inertia or.wing area. You'll see the result as a quick roll that you have to correct. On a plane twice as big and 3 times the weight, maybe only 1/5 of the wing area is affected and it's a much smaller force compared to the wing's ability to resist moving, so it's seen as only a little bump.