How important is the efficiency of a speaker to you?

My thinking is that efficiency is a product of both reactance (impedance and phase angle) and sensitivity. The reactance relates most toward 'easy to drive' while sensitivity relates more toward size of room to be pressurized. 

Since the Fritz speaker has been mentioned, I will add that Fritz speakers are easy to drive having a benign reactivity. A sensitivity around 88-90dB allows them to be played in smaller rooms with low wattage amps. As room size increases power requirement also increases however I can't imagine anyone needing more than 100wpc to drive them to their maximun output. If one is playing them that loud their room size/listening level likely is better suited toward a larger speaker.

I prefer speakers with a sensitivity range between 86-88 dB; I dislike those with a sensitivity higher than 88 dB because I want to avoid any hiss from the speakers. Contrary to the belief that high-sensitivity speakers perform better in low-level listening, the key lies in how you adjust the equalization to achieve a proper ELC.

Another misconception is that people believe high-sensitivity speakers can be driven by lower-wattage amplification and produce equally good, if not better, sound quality. There are a couple of reviews demonstrating that the Klipsch Cornwall IV (102 dB) can be driven with a higher-power amplifier to achieve better sound quality with more control throughout the frequency range than lower-power counterparts.

I went from 87 db speakers to 94 db speakers. Much better sound at low volume and less power needed.

@daveyf Wrote:

 When I mentioned this to the person doing the demo, i was basically belittled, as he felt that the efficiency of a speaker is pretty much irrelevant 

The importance of speaker efficiency: The article below is from 1962 and is as relevant today as it was then. In my opinion, a high powered amplifier that can drive lower impedances will never be a proxy for a speaker's lack of true efficiency. 

Mike

https://www.lansingheritage.org/html/jbl/reference/technical/efficiency.htm

A high efficiency speaker takes less watts to drive to the same volume level as a lower efficiency speaker.

ALL OTHER THINGS BEING EQUAL... If a speaker is 10 dB louder than the other, it takes 1/10th the power to drive to the same volume level.

The amplifier takes time to make this power (i.e., slew rate). So the amp "slews" 3.16 times faster to reach the same volume level resulting in increased dynamics for the high efficiency speaker.