I'm gonna vote Ketchup.
I enjoy both, but dislike both. Mustard I really only have on things like burgers etc, and not too much of it. Ketchup, the same but at least I can use it for fries and other things and it generally tastes better to me.
However, I strongly dislike the smell of both. There's nothing less appealing than when someone has eaten dinner and left a plate-full of ketchup sitting there so that the smell consumes the kitchen...I don't know how some people can drink bottles of ketchup, in those ketchup-chugging in food-eating contests....