As someone with lower back and neck problems I find it difficult to ride a road bike but I only really found that out after some extended rides. My advice would be to try out both road and hybrid, but not just on short rides around the block.

Is it possible for you to borrow or hire both sorts of bike, either from the bike shop or a friend, for a couple of days so that you can try them on rides lasting at least an hour? It is an important decision as the wrong choice could put you off cycling for ever.