You just asked a question that has a very very very long answer. I am going to simply say, yes there is a difference, try this sometime, play a song you know and change one of the chords that is a major chord to a minor chord and visa-versa and tell me if it sounds good. If it sounds better to you you might have stumbled across a secondary dominent chord and then it gets even more interesting. lol sorry theory is a blast. hehe