I think they differ slightly... they're all very strange and complicated topics
I think feelings are a lot clearer than either of them, they usually have a cause, and they're usaully strong and clear. Dreams and daydreams are more... dreamy? I'd say feelings are part of dreams, but dreams are too complex to be entirely fitted into emotions. They have an emotion 'attached' to them, but I think dreams are more than just emotions. And daydreams can be quite emotionless... (if you're daydreaming about corsework D: )