Która means "which", the ending of it suggests that the noun accompanied by this possesive pronoun is femenine, singular and Nominative (Biernik). This can be used when the answer could be limited to something you already know about like groups or sets, in a given context availability of something (among these [options], which one?).
Jaka means "what" but reffering to the description (could be simple as an adjective), this is as well a demonstrative pronoun and suggests that the object (noun) that tries to discover more information about is femenine, singular and Nominative, as well.
Well, we usually don't accept answers with this additional emphasis that 'do' creates... it sounds like "- Ci mężczyźni nie mówią po polsku. - OK, a którzy mężczyźni mówią?" (- These men don't speak Polish. - OK, and which men do?")