depends, if you go deception tree for an assassin, then yes, it plays a bit like a rogue. if you go the madness tree in assassin is plays dead on like an unholy deathknight (dots, death and decay, dmg buffs/debuffs to watch, etc).
more rogue like?
operative, concealment spec
more fun?
not sure, my mains a 50 madness assassin, and im lvling a concealment op, lol both are pretty fun and serve their purposes.