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

@tannoy56 you right about Tannoy 15" driver, this driver and also 15" JbL got very good bass response and good sensitivity, Bass is not go down like good sub. but still very good , especially punch bass, i can say this driver is exception from my post ,statement, i saw Scan Speak just came to market with new 15" Excellent driver with resonance 26 hz and 95dB, but still majority high sensivity  LS based on 6.5"  or 8 "  drivers  dont say true about  low frequency  and still need sub support

I use high sensitivity 100db speakers to explore flea watt amplifiers' midrange magic on voices and certain instruments.  The amp is a 8wpc 300B.

I'm not fan of low sensitivity speakers.

For economic and the large number of choices (easier to find bargains), I like mainstream sensitivity floorstanders that can be easy driven by 100-300wpc, extended linear neutral across frequency spectrum, well defined extended bass, sparkling highs, satisfying midrange.  

I have heard quite a number of big, high efficiency systems running multiple 18" drivers (e.g., Western Electric M10, G.I.P. reproductions of M10, Goodman 18" permanent magnet and fieldcoil woofers) and they deliver the speed, impact, and tonality that I think are most important in such drivers.  But, I have never heard these systems deliver really low bass at a high level.  I just don't care that much that they don't do subwoofer stuff and I don't really like subwoofers in these sort of high efficiency systems.  There are compromises in any kind of system one assembles, and these kinds of woofers deliver what matters to me.  Do they measure impressively?  I don't know or care.  I like Rolls Royce's specification of horsepower in the old days: "Sufficient."

I use most all types of amplifiers inc SET with a 6-watt SET I have horns outputting a solid 30hz and getting room lock. Those dissing SET never used them or they SET their system up to fail.