Not as talented as Vai?? Viz playing technique there's nothing to separate them. But as for the quality of tunes, Satriani cr*ps all over Vai from a great height. The great thing that separates Satriani from bigger names such as Clapton, Slash etc is that he can sustain high quality playing throughout one 5 minute tune to the next and not just the odd 1 minute solo here and there. I've also listened to a lot of other 'shredders' like Malmsteem, Tony McAlpine, Gary Hoey and loads of other similar widdly types. Sure they can play but boy are they boring! Just one Paganini inspired riff after another. To his credit Satriani's avoided all that pretentious and self-indulgent neo-classical metal tosh and doesnt let speed etc get in the way of the tune.
I've knocked one star off my original rating. Although there's no doubting his technical mastery he's come up with some pretty mediocre albums with Prof Satchifunkilus as bad as the red album and Engines of Creation, which IMO undermine his credibility.