I don't think I've done this yet, so. Sora's Sacrifice would be for when he's think about memories or is contemplative, or feeling anything deeply. But Sora's Theme would be his main one.

Anytime he's around or thinking about Riku or Kairi, Destiny Islands can probably be heard, however distorted it might be right now.

And being around or thinking about Jamie results in Standd By You. Not distorted since his feelings for Jamie grew while here and haven't been tampered with.