THD bellow 1% is really difficult to hear so both amps are good from that perspective.
Where we hear the differences is the FR as it changes depending on how the amp and speakers react to eachother while playing music. Specs are all manipulated by manufacturers and are mostly some tone bursts in easy 1kHz loads. They are basic guides but they don't even scratch the surface of what goes on when you play music with different amps and speakers. Specs used to be a buyers aid to help with system matching but during 80's specs wars they became just marketing borchures with brag numbers. But this doesn't mean we should ignore specs for system matching, but learn to filter the rubbish.
The D'Agostino amp looks alien submarine technology for interdimensional travel, but under the shell its still just an SS amp very similar to the CA. They both make small signal into big signal. However, they are similar like Citroen Saxo is a car and Ferrari F1 is a car.
It all depends on the speakers they are driving. Use both amps with a pair of cheap Sony bookshelf speakers and you will not apreciate the differences between the amps. Plug them in a pair of Focal Utopia's and you will hear the difference. While the CA will do an impressionist painting of the small signal fed into it, suffocating while trying to push the huge Utopia's, the D'Agostino will paint a stunning camera obscura like Caravaggio and frame it.