this Satch or Vai thing is a waste of time. If you like what they do then listen to them,that he´s better ,no he´s better is a waste of energy.
To be a truly great guitar player you have to keep an opened mind to all types of music and take in all the influences and sight and sound and make something of your own it,with your hands and express yourself through your guitar and that is what Satch,Vai,Hammett,Skolnick,malmsteen and many others are doing,being unique.
Instead of discussing who is better ,listen to there music and let them teach you from what they are doing.
peace out