Is the most efficient speaker the best speaker?

Not to mention personal preferences. Both in what aspects of music you listen to and your musical preferences. My own prefs lean to high eff, in part because of some of the great small power amps that can be run with them. Cost was certainly a factor too (though you can have megabuck or inexpensive systems with either set-up)

Right now the highest efficiency speakers are for the most part, horns. Most horns have more reactive drivers due to the fact that they employ greater precision in their voice coil gaps. This extra reactive nature tends to mess with amplifiers of lower output impedance, particularly those that employ a loop negative feedback loop- thus the idea that horns can be 'shrill' or 'honky'.

Horns also usually prefer an amplifier that makes constant power at all impedances (or at least *tries* to) rather than constant voltage. More info is at this link:

http://www.atma-sphere.com/papers/paradigm_paper2.html

So now we see that the idea of 'all other things being equal' taking on additional meaning! IOW you must be comparing apples to apples, so the other speaker of lessor efficiency should also be a Power Paradigm device. Given this constraint, if the higher efficiency speaker indeed is as revealing, has the same bandwidth, images as well, etc., then yes, the greater efficiency will be an advantage- you don't need as much amplifier power to make it go.

Since by definition we are talking about horns here, this is an advantage because the conversation makes no sense for the reasons I outlined if you don't also include tube amplifiers. The simple fact is that tube amplifier power is more expensive than transistor amplifier power. If you want realism (an orchestra can hit peaks of 115db to 120db), the ability to do this in a relaxed way without strain or harshness is then within grasp. It is simply not possible in most rooms if the speaker has low efficiency- too much is required of the amplifier!

Atmasphere is absolutely right. Horns rule. Lower power requirements equals more headroom and better dynamics.
Put your dollars into amplifier refinement rather than raw power. Quality over quantity.

Even speakers with efficiency an of 100 dB/W in a typical setting, will require about 200 Watts per channel to achieve 120 dB. One would have to have an extremely large room to adequately contain 120 dB with any semblance of scale, and require much more power in such a room than the 200 Watts per channel suggested above. Such power levels from tubes come at quite an initial cost, continuing costs, and some inherent technological considerations. Most people have neither the space, disposable income or even feel the need for such a luxury. Please don't get me started on the consequences of having to listen to horns in the first place.

And, they're off and running. . . Again.