The two amps would have to be compared in the same system for a comparison to be fair, and even at that, one amp would be penalized due to synergy issues -- arguably, the best comparison would be one amp in that amp designer's system of choice versus the other amp in the system of choice of its designer - in other words, "you made it, so show me what you think it can do".
It is fair to say that both amps are outstanding and show their respective designers' disdain for global feedback. Only having heard the darT (I own one), I might expect it to be somewhat more pure sounding on a highly resolving system because it features an unusually simple circuit (it is single-ended and uses only three stages) and each channel uses only one pair of output transistors, whereas the Ayre uses many more output devices, being higher powered and differential balanced. Being roughly twice as powerful, the Ayre may be better on unusually inefficient speakers. The darT punches above its weight class, however, and can do big orchestral on inefficient speakers known to be current-hungry (e.g., the original Salons). I have only spent an hour with an Ayre system, at a dealer six or seven years ago, but I thought it sounded outstanding.
