I have male/female littermates and the boy is way easier to live with than the girl. She is wild and thinks a throw rug is a pee pad. He is very calm and I don't see him marking anywhere except outside - and not overly so there. He is neutered, she is not. All dogs have different personalities. My two are attached to each other to the nth degree. They get along just great and hate being separated. They play together constantly. If your only concern is the marking, then I say to get him and train him properly and all will be well.
You will love having two playmates - so much fun to watch.