You're kind of making my point for me.
Edgar Martinez' top two seasons by WAR: 7.5, 6.5
Curtis Granderson's top two seasons by WAR: 7.8, 7.0
The other tools are meaningful.
However, I agree this is an open debate. Prospect rankings are kind of silly.
Martinez did it with his bat alone. Granderson was helped by defense.
Martinez's hitting > Granderson's hitting
Rendon at third (or second, or first) with Martinez type hitting is easily a 8-10 WAR player.