I trained in Tecnam high-wings, then transitioned to Cherokees and Warriors. I presently own a Beech Musketeer. I prefer low-wings for several reasons, but reason number (1) dwarfs the others: when I am holding short at an uncontrolled airport, waiting to take the runway, I want a clear and unobstructed view of the sky, especially a view of anyone who might be on final. I absolutely hate the restricted view a high-wing provides in that situation.
My other, less important, reasons are:
(2) Ease of entry. At my diminutive size, entering a high-wing requires stepping onto a landing tire or a strut or some such. Stepping onto the wing of my Beech is much easier, and I can set things like a kneeboard or headset on the wing while I sit in the seat and get things sorted in the cockpit.
(3) Ease of fueling. Dragging a fuel hose up a ladder, or even just climbing up to stick the tanks, is a royal pain.
(4) I've knocked my head on a high wing so many times that I'm convinced the only reason people like them is that they now have brain damage from one too many knocks.
(5) I don't like the way a high-wing obstructs visibility in the direction of a turn. This includes obscuring the runway during turns in the pattern.
(6) Low-wings look better. Don't believe me? Try to envision a high-wing version of a P-51. Just doesn't work, does it? Or a high-wing F-16, F-35, SR-71, etc., etc.?
(7) Low-wings are faster. Ever seen a supersonic high-wing?
(8) Low-wings fly higher. Ever seen a high-wing that will fly higher than the space shuttle?
YMMV, of course. Or you just might be in denial.