You haven't told us what you do with the rig. But generally speaking, you won't notice the speed difference between your options, nor whether you are 1t or 2t.
OTOH, while it should work its often more difficult to get 6 slots running well. While 3x4GB sticks should be easy to install, they also seem to put a bit more pressure on your mobo.
If you need 12GB, I'd take the path that costs the least or go the Corsair route if the price difference is meaningless to you.