I kept and Ocellaris in all of my tanks in the past, but when the last one died I decided to try something else and went with a Tomato. Unfortunately it has now grown quite large and is highly territorial, making it VERY difficult for me to place corals anywhere near its favorite spot in the tank...a rose BTA.
Like clowns101 says above, if you want an aggressive clown, go with Maroons...and I'd throw Tomatos in there as well, especially once they get big. But if you want a friendly clown, I'd go with Ocellaris. If/when my Tomato finally passes on or I am miraculously able to catch it, I'll be going back to Ocellaris.