What is your take on high efficient speakers vs. low efficient speakers?

I also prefer high efficiency speakers but they have big/many woofers to produce bass (Legacy Focus and Signature IIIs).  Noise is more prominent than lower efficiency speakers but so what, dynamics are easy to get, especially when loud.  I play my jazz and classical music up to 95 db all the time in a custom built listening room (expensive).   Average volume in the 80s db.   

Harbeth 40 series (top) speakers are rated inefficient with high impedance.  Relatively easy to drive with moderate power.  They never failed to sound excellent, especially nice in the mids.   At shows, no one says best in show but always musical as the mid-range is 90% of the music.   Much like Von Schweikert speakers.  I would rather own Tannoy's than most horns or stats (had stats for 20 years in my youth).   My wite of 24 years hated the big stats (ML Monolith IIIs) as they had limited dynamics, beamy, limited bass in particular.  I've moved on then to dynamic speakers and not return to stats ever (including good sounding Soundlabs).  

@mijostyn  I heard the Carver Amazing line array speaker.  No bass.  Wonderful spacious sound and imaging in the mids and highs.  Don't know if it would work in my room.   

I heard the Volti Rivals as did my friends at a show and stayed for 1/2 hour.   Most satisfying horn speaker sound yet.  

Best sound/music reproduction ever was the $1+ million Von Schweikert Ultra 11 and 9 at shows.  No demerits, sounded as perfect as I'd want for every time of music (agreed by countless reviewers/listeners over the years).  They are bigger moderately efficient designs with lots of drivers/bass.  The older designs were just as efficient but smaller speakers requiring only moderate power 25 to 100 watts (VR series speakers). 

@mijostyn --

The best performance comes from electrostatic speakers. They are generally mid efficiency speakers but are very amps sensitive and owner sensitive. Otherwise it is 6 of one 1/2 dozen of the other. The best performance I have heard come out of dynamic loudspeakers came from inefficient speakers driven by huge amplifiers.

One of the best setups I’ve heard comprise rather inefficient waveguide-fitted "dynamic loudspeakers" (S.P. Tech Revelation, actively configured and subs augmented). It’s the whole shebang; listening room, components chosen in every department, modifications here and there - just overall brilliant implementation by a guy who’s a total wizard in this field like none other I know. He assisted Bob Smith in the development of the S.P. Techs, has a tech background in electronics, years of experience in a high-end audio shop, crazy good ears. All this to say that whatever speaker principle he would be handed with complementary gear and all, he’d make it sound absolutely great I’m sure with mods and what not. It would be interesting though to see the absolute "level of perfection" he could wring out with whatever speaker principle he’d be given, but it’s a process that doesn’t come overnight.

Generally though low efficiency, direct radiating and not least passively configured dynamic loudspeakers (even with huge amps, which are really just a symptom of a severe bottleneck in the chain: the passively driven low eff. speakers) are at the bottom of my speaker ranking, then electrostatic speakers (which I haven’t heard actively driven nor as floor-to-ceiling height models like your Sound Labs), and at the top (no surprise there) are large(!) high eff. horn-loaded speakers, be they hybrids or all-horns. Those have been the best where they were fully actively driven with DSP filtering and solid state amps, actually, and not the perhaps more common pairing with low wattage SET’s or the likes as passively configured speakers.

You may feel inclined to give me the rundown on how I haven’t yet risen to the level of accuracy, but I’d dodge such a suggestion or even as a bluntly stated fact with mere indifference; I know what I’m hearing, I have my (live) references and preferences for how to rather effectively emulate such a ref. in vital areas, and not too few years of experience under my belt. I have my tastes (i.e.: preferences), sure - so do you - and the fully actively configured high eff. large horn-loaded approach just ticks off most of the core "pillars" in sound reproduction with the least bottleneck-feel to it to my ears. Even my friend’s S.P. Tech setup mentioned above, as great as it is, comes up short in several areas compared to my own ditto (and I’m just honest here; to hell with modesty), even though it’s not as well implemented overall as his system. Tonally though our setups are very much alike, which is interesting given the differences with our speakers in particular, but on the other hand it may not come as a surprise being that we share core sonic preferences, and also that he's been instrumental in the tuning process of my own system. 

lowest eficiency is bad for my single ended el84

In my opinion high efficiency for larger rooms. Less efficient for smaller. It all depends on the room which affects the over all sound. Klipsch  Horns in a 12x12 would sound awful.  In a 20x20 wonderful.  Also depends what's in the room.