While it may be impossible to choose just one "best" vintage set, for the sake of argument, I am going to state my top 5 reasons for why '57 Topps is the crown jewel.
1. Real life color photography taken of players in various "game-day" warm up routines before the first pitch. Fielding a ground ball, swabbing pine tar on the bat, laying down a bunt, it's all there.
2. A checklist loaded with stars and rookie cards, including over 10 major rookie cards, notably Frank Robinson, Brooks Robinson, Bobby Richardson and many more. In contrast, the '59 set has very few (with the exception of Bob Gibson).
3. Simple yet crisp design. White border with player or team name in yellow does not distract the eye from the main course.
4. Awesome player combo cards and other specialty cards . While this has been done before, the Mickey/Yogi Power Hitters is a classic gem and don't forget about the Dodgers slugger cards. Likewise, there is a Lucky Penny Card, Contest Cards, and a Gene "Bakep" Baker error card which make this set so unique, and by extension difficult, to obtain in its entirety.
5. The modern day card size was established/standardized by this set, thus eliminating all the awkward and random sizes, such as those tiny Bowman ones.
Well, there you go. Agree? Disagree? Look forward to the debate!