Loudspeaker sensitivity and dynamics: are the two inexorably linked?

I think one thing to beware of is that some of the high sensitivity speakers may also present a different frequency response.  It is not easy to adjust for both at the same time.  Meaning, we can't objectively compare a speaker that has the same frequency response as a Magico but horn, so we have to consider carefully what makes them sound different.

Another issue is often radiation pattern.  The controlled dispersion of a horn may remove the room effects, like ESL's can, leaving us with a very different presentation.

No, I don't think sensitivity and dynamics are inherently linked at all. There are some very inefficient speaker systems that are capable of remarkable dynamics.

Big conventional (dynamic cones in a box) type speakers can be "dynamic" in the   difference between loud and soft, with enough good amplification behind them. 

I use a hybrid- horns from Avantgarde but supported by additional larger subs in addition to the integrated woofers that come w/ the speaker. 

The key for me in this system is the amp- it enables me to use the Lamm ML2 which has a character that emulates real music. 

Using high sensitivity speakers requires a lot of attention to noise- grounding anomalies, other stuff that you would not necessarily hear through a less efficient system. 

It's a choice, like any other, in hi-fi. The big Cessaro, with bass modules, retailed for over 1 million last time I checked. 

I've heard Jeff's set ups-- he is the real deal, knows records. 

Speakers are just motors and should be treated like motors, but there are a few things at play. 
 

#1 power to weight of the amp/cone is key. Resistance of the drivers play into the power equation as does box size.

#2 air cupping of the driver. Larger drivers (or multiple) move more air with less distance traveled making them reach their peak throw need for a given SPL much easier. Also direct radiating tweeters are 2% efficient as they cut through the air where a good horn is 20% efficient as it has air more or less pressure loaded in front of the driver. 
 

#3. This one is just a guess as I am not sure. I think dispersion matters too. I think narrow dispersion speakers tend to be more dynamic all things being equal (sensitivity, surface area, etc.). Say a wide and narrow speaker of the same efficiency are given one watt instantly. The wide dispersion speaker dumps that energy into the room more than the narrow dispersion speaker. The narrow has more intensity on the leading edge of the sound. Think of a flash light with a focused lens vs no lens at all. Straight on the one with the lens is much brighter while the total brightness of the room when averaged in the same for both. Again just a theory.

While there is perfect correlation, it does generally hold that efficient speakers are subjectively dynamic.  The reason often given is less thermal compression.  With efficient speakers, far less current runs through the voice coil for a given sound output.  That means less heating of the wire.  As wire heats up, its resistance rises so the current flow is reduced — this means compression —the flow is not proportional to what entered the speaker.  Lower current flowing means less thermal compression.