It's simple lads Mike Mentzer or Arnold Schwarzenegger? Who had the better physique, who had the best training advice and program, and who would you train like most, if you were not on the sauce?
Mike looked incredible when he got that perfect score. Arnold got a lot because he had personality. Mike didn't. The one set to failure worked imo, when you were already in possession of a solid physique. Casey Viator was the case study for that, originally but again he a Champs build beforehand. I think a lot of bodybuilders over trained back then, and today it's stressed much more.
I liked the way that Mentzer looked, but overall I'd have to go with Arnold's physique. As for training, both of their principles are a little extreme for me, but I lean towards Mentzer's philosophy. Can't argue with either's results, though.