What do you prefer, grapes or cherries? Perhaps this is not acceptable because it specifies a person?
Yeah, the given sentence asks the question generally. If you want to direct it to a person it would be :
"מה אתה מעדיף/את מעדיפה, ענבים או דובדבנים?"
Could you translate the sentence as "What is preferred, grapes or cherries"?
That would be "מה מועדף". The word עדיף suggests it has some kind of advantage, that it's better - it doesn't mean it's preferred.
I would buy that
Can you say מֶה עָדִיף? But I suppose you do not use מֶה any more (it is followed by an unstressed עָ and מַה used traditionally to follow in its form the rules for the definite article).
How is this different from the passive