Alright, the reason why horizontals reign supreme over verticals: A: shorter throw, aka you have to lightly press them to get a click, and the distance they physically move before the click is MUCH shorter, as where a vertical pushbutton takes a bit more than a light touch, plus you have to keep a very constant force on the button to make it actually push. B: mashing, if you're going to be doing a qcfx2+kk with Ken in street fighter, and want to bust out all 15 hits w/ mashing buttons, if you can mash with verticals you're gonna be hurtin the next day. Horizontals literally feel smooth under your hands, and are MUCh easier to press.
Basically this is all I have to say, and this is from experience: for your next joystick or project, use horizontal pushbuttons. TRUST ME ON THIS ONE!! When you use the horizontals and try to use your verticals again, you'll be like "wtf....what are these things?"
-personal experience from someone who's super into fighting games, so I require light presses and what not.