Isner is 5 years younger and clearly has fulfilled his potential more.
Raonic's potential is probably better in almost every field except maybe the second serve. But not a lot better.
I think you mixed up the names.
Serve: Isner (the 2nd serve definitely gives him the edge, plus the pros agree with this)
Backhand: Raonic (both weak)
Movement: Raonic (helped by the fact that he isn't as tall)
Overall better player: Raonic