Quote Originally Posted by Meistro123 View Post
Playing 1 hand or 2 hands heads up makes no difference.
Playing multiple hands is another tool required to manage your proficiency and to manage your risk. It is not a "one size fits all", research it, understand it and use it.

In an oversimplification and excluding playing alone, playing two hands of a total bet amount equal to one hand (2X100 versus 1X200) will reduce your variance by about 25%. This is not insignificant.

Blackjack Attack has chapter with more specific guidance on this subject.