Hey mate. I'm currently working on a gladiator guide but it won't be up for a while.
The difference between bunny and gladiator is exactly what you said, champion = 1v1 with massive damage and guard to keep them alive (ideal for pvp) while gladiator I would have to say is one of the best characters for Pvm with berserk for bosses, lots of aoes for mobbing and can melle from range when they get chi sword. Search YouTube for "trickster online gladiator skill" you will see my videos there (lol at shit quality)
You other option is a hybrid which is a really nice combination of the 2. You get the best of the aoes from the warrior and the uber damage + guard from the boxer. You do miss out on chi sword tho and if you went hybrid bunny u would miss out on an extra ap buff as well as some fast dash+attack combo skills and a flaming fist which is element based and penetrates certain shields (I know it does dark barrier I'm not sure about any others)
Sorry for being brief, I'm in my phone at work