There are many more important things to consider than sensitivity. The change in relative output could simply be a difference in frequency response and wholly unrelated to the sensitivity. It's also important to consider how the sensitivity was rated as there are many things that can be done that makes two different "rated" sensitivities not directly comparable. I would look for performance within the intended bandwidth, distortion performance, how the T/S fit with your intended use, etc long before I considered sensitivity. As for drivers, what is your budget?