i think the op is asking a fair question, a somewhat technical question, he is doing something smart, which is to get his comparison process sufficiently rigorous so as to yield a result he can feel good about, he can trust
i remember as a 19 year old in providence r.i., working for one of the hifi retailers on weekends to make pocket money as a college student ... one of the well worn, ’experienced’ salesmen there kinda sorta took me under his wing, showing me what’s what in world as he saw it - the store had switching panels to connect turntables or other sources, to amps/receivers, to speakers, and then there was a volume adjuster
the guy boasted that he could get most anyone to buy system a over system b, by just making one play a touch louder than the other ... which he then demonstrated on a number of occasions
i’ll never forget that...