I'm not sure what you mean, but I would say that depends of context.
The major scale and minor scale are modes of the diatonic scale - Ionian and Aeolian, respectively. In a sense they're exact the same scale, but starting from a different note. They sound exactly the same.
If you pick C major and its relative minor (A minor) and play them in a way you could not tell which note is the root, you couldn't tell the difference because they're the same scale.
But if you play both scales "as is", like in an exercise, then they're quite different scales, as Dom pointed out. They have a different "feel" and they relate to different chords.
Also, C and Cm are obviously different scales because they have different notes.
I'm not sure what you mean with significance in your first question, but that seems to be a good question. I believe Allan Holdsworth would say there's no significance at all (between a major and minor scale that are relative to each other) if you're talking about improvisation, for example.