Ooo, I did my first joystick with vertical buttons, and it felt fine at the time, but i was always wondering why it felt so stiff. Vertical buttons are pretty much as loud as horizontals, and if you're control panel enclosure is made of stuff that let's sound out easy, you're gonna hear the clicks real well. If you made it from like 3/4" mdf and sealed it tight, you'd probably barely notice it.
The horizontal buttons use the same microswitches, but they have a shorter spring distance, and the actual spring is MUCh lighter on your fingers, when you from vertical to hirzontal, you're like "Ohhh, this is what all the pushbutton's are supposed to feel like." If you already got all your pushbuttons, and you don't mind em, then go with em and enjoy, but if you only ordered a few, order horizontal's the next time and you'll thank me.
-CthulhuLuke