The difference is not very clear and borders on the idiomatic, but I'd say that cuál implies that there is a known set of options from which to choose, while qué is more general. So ¿Cuál libro prefieres? implies that there are a couple of books in front of you and you need to choose from those.

English

The difference is not very clear and borders on the idiomatic, but I'd say that cuál implies that there is a known set of options from which to choose, while qué is more general. So ¿Cuál libro prefieres? implies that there are a couple of books in front of you and you need to choose from those.

Español

La diferencia no está muy clara y ronda en lo idiomático, pero diría que "cuál" implica que hay un conjunto conocido de opciones de entre los que elegir, mientras que "qué" es más general. Entonces, "¿cuál libro prefieres?" implica que hay un par de libros delane de ti y necesitas escoger entre ellos.

The difference is not very clear and borders on the idiomatic, but I'd say that cuál implies that there is a known set of options from which to choose from (so ¿Cuál libro prefieres? implies that there are a couple of books in front of you and you need to choose from those), while qué is more general.

The difference is not very clear and borders on the idiomatic, but I'd say that cuál implies that there is a known set of options from which to choose, while qué is more general. So ¿Cuál libro prefieres? implies that there are a couple of books in front of you and you need to choose from those.