To quote a famous philosopher:
...'In matters of opinion, debate is irrelevant' ...
So I am NOT going to generalize here, other then to say that speaker placement, amplifier choice and room acoustics have a MASSIVE affect on panel speakers more then anything else.
I currently own and have extensively compared ML Aerius i's to other designs - WITH AN OPEN MIND (I am not brand-loyal) - and just kept coming back to them after each audition as my speaker of choice *** IN MY ENVIRONMENT - IN MY SYSTEM ***. For the price, characteristics and availability in my area at the time, there was NO better speaker FOR ME. Funny thing was, I really did NOT want to buy these because of their potential limitations, but I didn't let that stop me, either.
Since purchase, I have moved from:
--Rotel to Bryston to Pass Labs x-series amps
--MIT T4 to Analysis Plus Oval 9 to Shunyata Lyra speaker cables
--REL Storm to MartinLogan Descent subwoofer
--Monster cable to Shunyata Aries balanced interconns
Each of these changes seriously upgraded the quality of sound the speakers are able to produce.
Now for the limitations of planar speakers:
--1 Location, Location, Location...
It's all about placement and room acoustics with these guys. I have a 30x20 vaulted room, but have better acoustics without special treatments then my dealer's best listening room - so Lucky Me. I also listen alone typically, so a large dispersion pattern isn't needed (focus and imaging is more important). Toe-in, distance between speakers, materials in the room and walls, etc. - ALL affect these speakers dramatically. You may NOT have an environment that can tolerate these conditions, so an in-home audition and alot of experimentation with placement is the only way to tell. Little adjustments can make big differences, especially in stage width and lower-octave response.
--2 Amp synergy...
Though rated at 200WPC max, these speakers REALLY like power. They are a difficult load, going down as far as 1.2 ohms at 20KHz, so a high-current amp is essential (one that is rated to fully DOUBLE power output from 8 to 4 ohm and preferrably again from 4 to 2 ohm). The Pass Labs x-series amps are balanced, differential designs with Zero feedback, which helps too. They are slightly warm-sounding, which further helps the Aerius as they can sound harsh & fatiguing when driven by certain amps (like Bryston 4B-ST's, as I found out).
--3 Speaker cables...
I found out the hard way that these speakers HATE the lower-end MIT's Terminators. They really killed the synergy between the speaker's woofer & panel. My Analysis Plus fixed alot of that, opening up the lower octaves and adding smoothness, and the Shunyatas add yet another level of detail, dynamics and stage depth.
--4 Gotta Have a SUB...
Significantly, without a dedicate subwoofer, ML speakers are missing the lower octave information that acts as a foundation to support all other frequencies (Aerius do not work below 40Hz). Without a quality sub, I agree that the soundstage IS smaller, the dynamic range IS compressed and the internal 8" woofers are noticeably hard-pressed to keep up. REL & MartinLogan subs are especially suited to help in this regard - and this affect is instantly distinguishable by simply turning the sub off/on and listening for the stage to expand/collapse. So, moral of the story is: unless you are a real sub-hater, get one when using these speakers.
If you are still interested in the Martins, I recommend that you visit www.martinloganowners.com and ask some more specific questions.
I hope that helps, -BUT- remember ...Your Mileage May Vary...