In my personal opinion, TH is probably more fun to play. You simply have more skills to play with, like silent move (great for getting to a party which is deep in a catacomb), fake death (great for training that party if you do not like it), lure/switch/... (switch e.g. works on players and removes their target, very handy), the insanely powerful backstab and the other dagger specials which make you very very deadly in pvp and you are welcome in most parties for very high and consistent pve damage even without spending any mp. Sure, high lvl Gladiators are very powerful, too - but I simply think a TH is more versatile.