Difficulty Level and Mission/Chapter Scoring

Just curious, but apart from changing how resilient the enemies are, will playing and completing the game at the 3 different difficulty levels mean anything more than just an added challenge? Examples would include maybe some form of an "unlock" or bonus.

I only raise this question since I've noticed the game tracks whether or not you've completed the mission/chapter on a certain difficulty level. And it just feels like that it should lead into a reward for players who take on the game at all of the difficulty levels.

I am also curious about scoring. Is it mainly a cosmetic feature or will it end up meaning a bit more to players? Maybe high score numbers that will be used in out-of-game contests? Tied to possible "unlocks" or bonuses?

I understand that there are probably some things you guys and gals would like to keep under wraps for future things (and to not possibly spoil some surprises), so if this inquiry cannot be answered...maybe give us a tease? :p

I find the math of the scoring confusing, due to the lack of plus and minus signs. For each teammate that dies, it should take away from my score, which I guess it does. But, having the plus and minus signs would help.