Even though they are different, they have been on the same label for some time, they lived in the same town, they have learnt guitar together (Satch said they jammed more than they actually did any formal training), and most of all, they are on the same rack in stores: instrumental rock, or guitar instrumental.
Satch comes more from a blues background, while VAI has developed into this Jazz/experimental music... But I guess it's fun to compare them both...