pure class A's selling points were low to non existent notch distortion, imo the jury is still out as to whether this is audible vs-a-vis a high quality A/B amp. The reason others like me used them was the stability into any load to almost a dead short, and the succesive double of power with each halving of the impedence. Ive owned Soundlab electrostics that posed a 1-ohm load at high frequencies, the amps i used were krell ksa-250 and mda-500s but Rowland 7s (class A/B) worked just as well. i have direct experience with all non-reference series krells up to the early '90s, since then Krell have become high bias A/B but still deliver high current.
to stir the pot some more, the biggest proponent of class-A, the guy who spent 30-yrs building his reputation on it, now only builds A/B amps (low bias at that) and says it his best work ever (D'Agostino)