I'd don't think we know anything of note about Morata's talent.
Has he played an important role in any of Madrid's big games? Only big game I have seen him in was the Cl final and he didn't really do a thing when he came on for the useless Benzema. What I have seen of him involves decent movement and heading, is that enough for us to train him up on loan for Madrid?
Also, if he is any decent you know what sort of DNA he has. Real will get him back for a minor figure as they will tap him up every year in the media and spanish team. I see no point in going for players from madrid or barca unless: A) they are young and on a real cheap deal (compo) B) They have been driven out of the club as a senior player and won't be in a hurry to return.