A lightsaberstaff and two-lightsabers are purely only ment for battle, these kind of lightsabers are only good for Sith assassins whos sole task it is to eliminate the Jedi. That is why it suits Darth Maul very well, he had to confront two Jedi, one of them a Jedi master btw. Dart Maul won against Qui Gon because it was pure battle based and he could attack him at two places at a time. Once Maul's sabre was slashed into two peaces he wasn't that powerful anymore.
Two lightsabers is no good at all, you don't have a strong grip on your saberhilts and you can quickly lose your grip on them. Like what happened with Anakin.
Using one lightsaber with both hands you can use your maximum power in attack AND in defense. You can concentrate more on your opponent(s) then on your own lightsabre. Your are more precise. You need less training in the use of the lightsabre and are equally good with it. Less time making your lightsaber, you're better of wasting your time on life-experience and force powers. Your defense is extremely better. And you have better control on saberlocks because of your strong grip.
And you've less change of hitting your friends in a multiple dual (see the game: jedi academy).
So the lightsaberstaff and two-lightsabers are cool as one-time-events,
and the lightsaber is the Jedi's weapon.
PS: the battle between Luke and his father are the best lightsaber duals, not only because of the battle itself, but also because it is between a father and his son. A conflict between father and son is the most sensitive subject in the world.