I'm in the process of making a speaker selection, though frankly my speaker knowledge is admittedly limited. A friend of mine is a physicist, and also a pretty good and experienced musician. It's his opinion that sensitivity is the most important spec for determining speaker fidelity. The argument goes that for a given amount of power going into the speaker, all that power needs to come out. If it's not coming out at the intended frequency (which you measure via a sensitivity measurement), then the power must be coming out at other, nearby frequencies / harmonics that are not intended, i.e., you have distortion. This seems like a good argument, yet I've read elsewhere that sensitivity has little to do with fidelity -- that it's just a measure of the efficiency of the speaker.
Anyone care to take a side?