i think he would have fewer wimbledons. Sampras would have taken a couple off of him for sure, if not splitting them almost evenly.
probably compensated for the fewer wimbledons with more RGs and more AOs and certainly more US Opens.
Agassi wouldn't exist. To have both Federer and Sampras beating up on him would have been too much. Probably would have ended up being a good baseballer, or TV actor.
Disclaimer: I'm NOT a coach...
Real tennis: https://www.youtube.com/watch?v=yDqnkLJ9BtM