The first thing my coach taught me was the stance. He showed me 2 different stances. One stance was at shoulder width apart, which you can move in all directions which is the attacking stance.
He also taught us the single stance or the single line stance which is more a defensive stance. Which you can cross block and shoulder roll out off. But is harder to throw a right cross unless you step your lead foot across into the attacking stance as you throw the right cross.
I dont think you should choose one of the stances i think you should use both, depending which one will give you better balance in the situation.