The riding position of FBRB is not neccessarily upright, you can set the bars to be quite sporty if you like. You lose the variety of positions and gain some nice controls.
Beware that some designs of FBRB are too RB for commuter use. I have seen them with short drop calipers which lack clearance for medium tyres and fenders. I have also see ones lacking any rack or fender eyelets.