Then I would think,
1] majority opinion rules, if 5 say bad and only one says good, the preponderance is with the majority.
2] If it is probable that the one maintained and didn't abuse, where the others didn't maintain and did abuse, I'd still lean to 1]. Engines should be able to handle some "work", per se.
Meaning, using them hard at times. But I am a stickler, or try my best, to keep an eye on the engine of my rides. So, I feel confident of using my engine hard at times.
Is there by any chance, any recall issues, or problems occurring at certain mileage than you know of?