I don't think Morata is ever gonna be as prolific as Higuain is. But if he gets to the level of scoring 10-15 league goals per season and in addition remains decisive in important CL encounters then I'd take him any day over Higuain.
If he goes to a place like Napoli where he is the main guy in an offensive team or was given a starting spot in a free scoring team like Madrid he should score much more goals than with us. I actually see him as being very similar to Higuain in the near future and without having wasted his time at a place like Napoli not getting any trophies.
