Going off topic again.
Overall musicianship would go to Buckethead. He plays guitar, bass, mandolin, banjo, bouzouki, drums, synthesizers, percussion. He also has composed soundtracks for movies.
Buckethead
Genres: Avant-garde, noise rock, funk, thrash metal, bluegrass, instrumental rock, hard rock, progressive metal, heavy metal, progressive rock, experimental rock, funk metal, ambient, dark ambient, alternative metal, electronica, country rock, folk rock.
Steve Vai
Genres: Instrumental rock, hard rock, heavy metal, progressive rock, progressive metal, experimental rock.
So when it comes to deversity and musicianship. Vai does not have him beat at all.
Compostions and feeling are debatable since well they are based on one's taste. I may feel something from a song by Buckethead more then I would with Vai, but for you it may not be that way. It may be reversed. (last sentence being the case.)
They are both great and both are extremely talented.
I'll take Buckethead over Stach and Vai anyday.
I do like Vai though especially his work with Zappa and also what he did in Crossroads (the only reasons I voted for him). Though I do tend to find Vai extremely boring.
I do enjoy Satch as well.