Good questions. Actually the performance slightly favors the "double" models as these essentially have twice the output device die area of the standard units. The "H" versions have 50 percent more die area than the standard units.
Of course the real killers are the "Double H" versions with three times the die area and current capacity as the standard Insight 260 and 440 models, probably the best you can find to drive really nasty low impedance loads.
Note that we have only had two cases of failed output mos-fets in any of the single die standard versions using the Exicon devices and those were both from extreme overdrive situations.
Best regards and have fun choosing.
Frank Van Alstine
P.S. Our web site is a bit obsolete right now but that situation is nearly corrected. There will be a new version of the AVA web site up and running within 30 days with all the newest stuff described.