Were I playing (which I'm still in the gray area about) I'd like to be able to switch between 2 saber, single saber, and double bladed. Period. I doubt if they will give very much emphasis on the lightsaber forms aside these varints and I suppose that's fine, but I would want to be capable of utilizing each variant without severe penalties because switching around is a matter of pragmatism. Different situation requires different armament.
IRL it depends on the sword or swords you are using and the opponents you're facing. Darkkender is pretty much right, though, 2 blades or double ended weapons typically were more aggressive. But it depends what style you're using and what style your enemy is using. Larger blades I can say this is so.
In sabre & rapier fencing, though, 2 blades increases both your defense as well as your offense since you constantly have to switch between defense and offense anyways.
Miyamoto Musashi developed the 2 blade style of katana combat. He believed that while there were some maneuvers that required 2 hands to execute, you [otherwise] should not need to use 2 hands. Offensive and defensive. Obviously every weapon has its attributes, pros, and cons.
I don't know the mechanics of how games will be but I think the way it has been like in KOTOR 1 & 2 worked well enough: 2 blades increased both offense and defense (in some respects more than others), but it might perhaps leave you weak on the front of vs. force powers.
That's right, Bixby Snyder folks.