Sonically the M-500t won by a hair.
Electronically the M-1.0 has much cleaner looking clipping.
the M-1.0 rails (3) switch like rungs on a ladder, when the signal reaches the limit of one rung the next higher rung/transistor switches on; with the M-500t rails (2) switch over the heads of the same output transistors, raising the voltage over their heads, so it's one rung that gets wider.
As a conseuqnece of it's switching style, the M-500t at clipping seems to have artifacts from ALL the rails happening (four smeared looking horizontal clipping regions at the top of the waveform, two on the way up and two on the way down) and the M-1.0t clipping looks more like 'regular' clipping.
Given that behavior, from measurements I SHOULD prefer the M-1.0t, but I don't. The ONLY (and possibly far off the mark) reason I can dig up for this is, since the M-1.0t transistors aren't 'on' all the time, like the M-500t's are, that early effect is somehow coming into play.
As far as taste goes, having lost my left cerebellum drastically altered my sense of smell and taste (I know you didn't mean tongue taste, but it's an interesting (to me) fun fact).
Regular food now tastes WAY too sweet, to the extent that dinner rolls (for example) now taste and smell nauseatingly sweet. In the olfactory, my left nostril no longer responds, to ANYTHING; which is a bonus when you're changing your daughter's diaper