i depends really, if your going to become an actor, artist, musicion etc then imagination is far more important, but most jobs require knowledge more. My school focused on drama, sports and music a lot, but thats bcoz we were all stupid and couldnt do maths lol.
Saying that, i believe playing an instrument makes u use a seperate part of your brain. It sounds crazy, but when i play my guitar i have to read music, control my right and left hand at the same time and its hard and i also hadnt played it for about 2 years, i picked it up again and my fingers naturally played the song, i didnt really have a lot of control where they were going. Now i sound mad but you'd have to do it to understand it lol.