I am also a fan of horn speakers because of the superior dynamics, vivid sound and ability to deliver a soundfield that is large an enveloping. Most horn systems, even though they are large in size, can fit well into smaller rooms because of their controlled directivity. The higher efficiency of horn systems allow one to use the very best sounding amplifiers which are, in my opinion, low-powered tube amps. The combination is magical.
Horns are more efficient not just because of their directivity, but primarily because they allow for more efficient transfer of the force of the movement of the diaphragm to the air. Air is very light and offers very little resistance so energy cannot easily be transferred (think of how hard it is to throw a feather). The mechanical resistance of the air is increased by confining it in a space to be compressed by the diaphragm. Compression drivers utilize a small chamber behind the diaphragm to greatly increase this resistance and improve transfer of the energy (not all "horn" drivers are compression drivers, some have horns to act primarily as a wave guide). Higher efficiency means lower amount of current running through the crossover and voice coil for any given volume level. This reduces heating of these components. Heating results in "thermal compression" where the higher temperature means increased electrical resistance and less current flow, and therefore less speaker movement than if the wire is subject to less heating.
There are other types of high efficiency speakers that share many of the good attributes of horn-based systems. One can find single driver systems in quarter wave backloaded horn cabinets that are remarkably close to delivering a full spectrum sound and reasonably high volume levels. I have heard, and like very much systems by Songer Audio, Charney Audio, and Voxativ. I have also heard impressive systems utilizing fullrange drivers in multi-way systems so that another driver, or two, handles the extreme lows and/or highs. The Cube Audio Nenuphar Basis is a good example (fullrange for mids and highs, powered woofer for the lows).
As for the choices mentioned my the OP, I like all three choices. The Rival, in particular sounds good. The Volti speakers are particularly nice sounding, although the Razz does not quite do integration of the woofer and the upper range quite as well as I would like (still, a minor issue to me given its virtues). The Cornwall can be a touch rough sounding, but, it, like all three of these speakers, can be made to sound very good when using the right amplifiers (meaning good, low-powered tube amplifiers). These are not speakers to stint on the quality of the amp.