It depends what you are trying to do. There are a lot of moves that involve slipping or parrying outside a left jab and stepping across his lead foot with your left foot; you can hit the body with the left hand from here, or simply step past him, then pivot around behind him. A short step like this, with the left foot, will put you in a position to follow his left hand home with a right.
And, of course, you don't need to step at all. Drop your weight onto a flat right foot to slip the jab, which is the same motion as throwing a left hook to either the solar plexus or the chin. A very short punch but very possible to get a lot behind it.
Personally, I favor a small movement to the right with the left foot because it keeps you in range, better, I think, than stepping to the right with the right foot.