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

I would be surprised to learn that designer would, keeping all things equal, purposefully forgo efficiency to arrive at an 87 db or lower sensitivity.  In other words, designing a speaker that has 90 db efficiency and then padding it down strikes me as bizarre.

This reminds me.....there are lots of anecdotes of 70s/80s era IBM mainframe customers seeking more processing speed, and IBM sending techs out to *remove* a board from the system.  Still makes me laugh.     

There is none only if you like 300b 18watt amps its all personal taste and a well matched system.

In general the main reason to design a less efficient speaker is to enable more extended bass out of a smaller speaker. This has been the popular trend for the most part ever since higher power SS amps started to make their mark.