I don't have anything bad to say about the Harmons. They are great planes too. But there are significant engineering differences between the two airframes. That doesn't necessarily make one superior over the other, just different.
Just because they look the same doesn't mean anything. To me, a Porsche and a VW look the same, and they are built by the same company, but I know they're not. Just in general terms, the F1 airframe was designed from the ground up with thicker skins, joggled joints, and is beefier all around. It is designed to handle the IO-540 and the speeds it generates.
I like most, if not all airplanes and I love all Rockets (F1, Harmon, RV-8, etc). All are different ways to get to the same place and offer lower cost airframe alternatives than the F1.