Haven't played as a Jedi Knight before, but speaking from a Jedi Shadow's point of view, I say you go with that. If you use it well and get good armor, you can easily take down almost all enemies. They get good stealth moves to avoid some mobs, and of course since it comes from the Jedi Consular tree, you get the Force Speed move, which comes in handy. As for a Jedi Guardian, I have no idea what they actually get, but my friend is playing as a Sith Juggernaut, and I suppose they get the same moves as a Guardian. He hasn't shown anything interesting so far (we're both only level 29), but I think they might have some better moves.