Hmm... well for some people Competitions are much better because you feel the corners a lot more, but my problem with them is that games like Snk vs Capcom or King of Fighters 2002 your doing a lot of SNK style'd super moves. When the joystick is constantly sticking to the corners, its way harder to pull off a terry's power geyser. So it's all bout the style you play, I personally use supers on all my sticks, although perfect 360s are by far the best, but I dont have that kinda money to throw around. So I'd suggest supers if your good at knowing where the corners are and play a lot of games that requre a lot of half circles, and more SNK style moves. If your playing like ONLY street fighter games where your doing uppercuts, fireballs, and half circles only, competitions work great for that.
In terms of buttons, that's also a feel thing. Both horizontals and competition pushbuttons *concave and convex* both have pretty light springs so they're easy to push and what not. The competitions are smooth so its a little easier to mash, but the horinzontals are pretty much just as easy. The horizontals feel good for fighters and old school games, so if your going to be playing any older games, get horizontals, but if your sticking to fighters competitions are a good bet.