With a bent your neck is held in a much more natural position. On my upright bikes I find myself looking down at the tires in an unnatural position and develop neck stiffness (which can trigger a migraine) and low back pain.
Did a 15 miler last night on my comfortable LWB bent last night and felt so comfortable I asked myself why I would ever even consider the upright again? (a bit easier to transport) Besides, wearing boxing gloves and diapers doesn't appeal to me.
May or may not work for you. Borrow or rent a bent and try it. I'd hate to make a blanket statement about everybody's neck, but several of my friends have gone to a bent to get unbent and swear they'll never go back!