Apart from speed constancy, which you addressed @frogman, it is hard to isolate what the turntable is doing in a system, leaving aside variables in arms and cartridges (a subject that was recently addressed in another thread about how people can ’hear’ a turntable in a ’drive by’ listening session without also taking those other variables, including the system, into account).
My go to, to start, is Janis Ian’s Between the Lines, standard issue Columbia pressing- it has female voice, real horns and strings, plus electric instruments and a range of styles, to give me a sense of sound. But, I would also use other records to compare- and none of them audiophile spectacular type albums- i'm more interested in what the front end brings out in a ’nothing special’ pressing- though some of those mentioned, like the early Vertigos of Sabbath per @atmasphere are impressive on a good system.
My go to, to start, is Janis Ian’s Between the Lines, standard issue Columbia pressing- it has female voice, real horns and strings, plus electric instruments and a range of styles, to give me a sense of sound. But, I would also use other records to compare- and none of them audiophile spectacular type albums- i'm more interested in what the front end brings out in a ’nothing special’ pressing- though some of those mentioned, like the early Vertigos of Sabbath per @atmasphere are impressive on a good system.