It must be a horses for courses thing. I just tried out an even taller stem for my upright, and if I'm sitting too straight, it gets really uncomfortable to pedal and maneuver the bike. For me, swept bars are the most comfortable, and have eliminated the need to change positions.

In a sense, a bike is an adaptation of our bodies to the environment, and we all have different bodies, so we end up with different ways of fitting our bikes.