Seems like there's a lot of younger people on this site. I'm fifteen, and so is Geo. =P Teens learning together, what's cooler than that (haha uber nerd). I had the same delema. I love the maroons to death because of the way they swim. They look like flags, but I decided on the percs. My LFS had babies, and I couldn't resist getting a pair. Named them Ponyo and Sosuke after that movie, and I wouldn't trade them for the world, or a mean little maroon.
Maroons are extreemly territorial, and need a relitivly large one. In a small tank like you have (I have a 29), I read that they will claim the entire tank as their territory and bully everything, especially your hands if you put them in your tank for whatever reason. Put a new frag in, they'll probalby knock it over. New fish? It'll be terriorized. They kind of remind me of those steriotypical high-school cheerleaders. Beautiful and mean.
I also hear from some people that percs hug corners. Mine, personally, won't stay still for less than half a second and constantly swim from one side of the tank to the other. They sleep in caves during "lights-out" and as soon as the lights are on they swim up to the front looking for me, and follow my finger around. Very cute.
Good luck with whatever you choose, though I recommend the percs. =)