I'm afraid I must disagree with you when you say Vai makes people believe that he's better than Satch. Unless of course you'd call For the love of God a marketing-trick..
We can just listen to both players' records, (to compare easy they do 'Feed My Frankenstein' :-)) see them on stage (they do G3) and try to copy their playing (almost everything is available in TAB/writing). So we can judge from what we see and hear.
But hey guys, it's not like you have to dislike one when you like the other. I'm a huge Satriani-fan, even played Always with me/you on my wedding!
As for the teaching, I think Bardsley tells the story as it is. Satch is proud of his one time pupil, and Vai takes every opportunity he gets to express his gratitude.
And so he does with Frank Zappa, another major influence on his playing/songwriting.
Thanks for the lead on Ron Thal. I'll check him out.