Both are overrated. Mata is a lazy bastard and everybody knows it.
Not lazy, but doesnt work hard on defensive duties, but why should he? He is a creative attacking player who's job is to create and get into scoring positions when able.
I dont get why everyone has to be this mad pressuring and tactically suited player. It helps if excell at that, but not everyone has to be like that, there should be room for players like him, especially when he does his job spectacularly effective when used as he should be (Oscar works hard, but what good does that do them when he cant even create even a fraction of what Mata did?). He is a Nr 10 attacking playmaker, shouldnt need to be more, no one was more effective assist giver then him more or less in his Chelsea days, and his efforts lead them to winning titles, thats why I consider him a world class attacking midfielder.