Could vs Would vs Should?

Just remember that could is used to talk about something that can happen, would is used to talk about something that will happen in an imagined situation, and should is used to talk about something that ought to happen or must happen. I hope this helps.

Could you VS would you?

'Could You' is considered to be an informal way of asking something, contrary, 'Would You' is a formal way of requesting someone to do something.

Is could or would better?

But I would suppose that “would” is more polite, because it expresses the idea of probability, and of willingness, and of the desire that something be done, whereas “could” is more in the realm of ability (yes I can). And according to the American Heritage Dictionary, “would” is used to make a polite request.