Horn coupling is great for efficiency but generally a weakness when it comes to transient/impulse response. -They're usually VERY impressive if you're impressed by apparent acoustic 'size', but they invariably sound awful to me. -Actually there was ONE set which was built by a designer in the central valley area of California which sounded pretty close to me, but even so, I had to tell the builder that they were the best HORN LOADED speakers that I'd ever heard, but that sentence is only true with as long as you keep the words "Horn loaded" in there.
line arrays generate part of the appearance of lower acoustic output falloff with distance by cancellation at closer distances and more efficient spectrum-wide adding/summing/reinforcement at greater distances... translation: the closer you get, the worse they usually sound. They generally find use in cathedrals, arenas and other areas where the acoustics are so terrible that anything else would be a washy, echoey nightmare. -In comfortable acoustic rooms I've yet to meet a set which didn't sound deeply flawed, and until they repeal some of the laws of physics, I doubt I ever will...
In short, line arrays are handy for lousy environments, but part of what makes them work is what makes them sound so terrible to my ears.
Every speaker design has flaws and problems, and each approach usually has sinificant advantages. -For most people, the traditional cone woofer/soft-dome tweeter approach is the most acceptable compromise. -For me it's the electrostatic approach, with perhaps an LF cone woofer crossover, a-la Martin Logan. These bring a serious acoustic challenge to controlling what comes out from the BACK, but are unmatched in terms of detail. -I only wish my wife would let me bring a set home.
Keith