For myself, I don't think either is harder to fly than the other. It's a matter of experience, or, can you think faster than the plane can fly and make corrections without really thinking about it. Low wing planes tend to be designed to be faster, it's not an automatic that a low wing will be faster. Dihedral, yes, for stability, and it does work. But dihedral can also make for strange looking rolls, so the low wing will probably have less. In the end, it comes down to the way the plane is set up, and the man with his thumbs on the sticks more than wing location. I tend to more like both, high and low, on the same plane at the same time.
Rich.