Is there any advantage to lower efficiency speakers? 87 or below?

I wish I got 18wpc out of my SET 300b. Gosh. 8wch lol

i think ( and I know the origin of the J Cash comment - seeking to FIRST replicate a live unamplified reference one is VERY familiar with) there are two camps here:

1.) build a full range speaker that comes as close to the reference as possible with manageable efficiency as an outcome. 

or

2.) add efficiency target value into the important parameters list. For all kinds of reasons: small amps tend to be affordable, some customers like hearing damage, the 300 B ...First Watt....fill in the blank)

what i find more interesting is all the in and out of phase junk that gets counted as output.....

Mmm, duplication of 'live' is such a 'moving target'.  Since one is listening to a recording of a live performance (for example) that's gone through myriad equipment and processes in the interval.  It seems to me (IMHO time) that the only way one could really make the comparison properly is to have been at that performance.  And even then there's the contrast of where one was sitting, one's state of mind, and the influence of memory.

*Sigh*  We're left with attempting to recreate as best as one can our opinion of what it sounded like, or should sound like...in an entirely different space.

Studio work boils down to the artist(s) working with the engineer(s) to make the work sound like what's in the artist(s) mind.  There's a certain simplicity in that...

We can either approach that reproduction with either 'bare bones' or a more complex combination of items.

Either way, it comes down to what sounds good to you.  And the guy next to you will think it sounds like dreck and you're brain damaged or have a hearing malfunction.

*L*  And we're right back to 'what sounds good/right to you, and the enjoyment of that.  And 'twas always thus, and will always will be.

MHO and yours....;)  May not or never be the same, but many things are like that...

how much live unamplified music is in your listening diet ?
and then with a good mic or two before the tape heads or after ?
try that a bit
but yes we all have our opinions

 A lower sensitivity speaker will block more noise contamination than a higher sensitivity speaker.
 Often times a speaker designer will sacrifice some sensitivity for other considerations.