To again try to add some clarity. The type of bars really should not affect your comfort, the way the bike is setup and how you ride the bars may. Riding on the tops of a drop bar is no different than riding a flat bar if the relationship between the seat and bars are the same. Many times though drop bar bikes are setup more aggressively with the seat higher and set back farther than a flat bar bike. Riding on the hoods or in the drops stretches you out making you more aero as it is designed to do and that will require more muscle tone in the back and neck. Make sure you seat is setup so that your center of gravity means that you are balanced and not leaning forward or back which will contribute to muscle problems. If your seat and bars are setup correctly you will build up the muscle tone necessary to ride in the drops after some practice.