There HAS to be a pressure difference or there's no lift. However if you did the search I suggested you'll also have found that along with the pressure difference there's a redirection of the airflow mass that also HAS to be there. These two are linked and interdependent and are an integral part of any surface be it flat or curved or a spinning cylinder (magnus effect) that is generating lift.

So why do we fret over airfoil shapes so much? Because an optimized shape can generate the pressure differneces and airflow re-direction that goes with the pressure difference with the least amount of drag. And when we can do that with less drag the model flies better...... at least it does when it's a glider or sailplane. SOME models such as 3D stunters WANT the huge amounts of drag that come with sudden and extreme angle of attack changes.