You will get a slew of answers to the effect that it depends upon measurements. But, that doesn't guarantee an amp will sound good. It's been known forever that tube amps typically have more distortion, but many love the tonality despite them being less clean.
One man's "clean" amp will be another's "sterile" amp.
Expect many recommendations of favorites purportedly clean amps. This, as well as any other parameter of sound quality, is on a spectrum - a wide spectrum of performance.
Just compare a few and go with your favorite.
