Many (not all) panels ring, they have poor damping qualities, negating the faster rise time. Also most "panel" speakers overshoot on transients making them edgy and unrealistic sounding and bright. Stock Maggies can be this way but never to where they are "bad" sounding.
Dynamics are restricted, and when pressed all but the very best panels "Fold like a Baby" using the words of MLB Ray Lewis.
The panels need to be large to sound good, which can make placing them optimally in a "typical" to a below average size room more difficult.
If you're only going to have a two channel system the dipole is the way to go, but they completely ruin the effects of surround sound.
My message only the "best" panels rise above your generalization and so do the best box speakers for that matter. Problem is recognizing that the "best known" speakers are not the best speakers by defacto.
Due to the 30+ years most "panel" speaker companies have existed the best panel speaker companies have survived and by almost default have become the most well known. So people buy the best panel speakers much more than people buy the best cone speakers which is dominated image wise by under-performing over the hill superstars.
Cone speakers have yet to go through survival of the fittes. Panel speakers are obsolete relative to the mainstream audio markets needs, which restricts them to the specialist markets, thus all they make is specialist speakers.
