I think Gambler is better.
Since I only play female characters I made a Diva, if I were a guy I'd make a Gambler for sure.
-They grind faster.
-FH/PC are both really good skills to use in PvP/GvG situations.
-Bulky since most will go HP.
-FH fails and you get damages.
-Need to carry lots of pots to keep up FH/PC full power.
-Very good defense with sumo suit.
-In PvP/GvG situations, Rust wouldn't affect as much if you have very high HV.
HV also improves the Magic Melt down skill if you fight a mage.
-Doesn't have FH/PC (Which stuns), I find the AoE skunk version not so useful. In PvM/Boss you will hardly need it at all. In real PvP it is kinda a slow skill. In GvG people tend to spread out in the area...it is hard to land a hit on a mob... You'd still need to rely on basic skunk.
-Bad AoE skills. Only 2. And siren song isn't very good for grinding. In other words, you'll be slow grinder too.
In both cases, boss hunt wouldn't be a problem as long as you have a guardian that knows either Guard break or Shield Break.