I am going with the 2 lightsabers mainly because I have always thought the double bladed saber was kind of dumb. It looks cool, but the design loses almost all the advantage that actual long weapons give in combat.
I'll have to agree. The doublesaber has two dangerous ends which limits what moves the user can actually make without cutting himself, and it's not really long enough to give much of a reach advantage vs a normal saber. A parried swing might end with you cutting your own arm off, and you'll have the other business end in your own chest if you try to reach too far.
If it was something different - a spear or naginata styled polesaber - then I'd see how it could be very dangerous against someone with normal sabers.