Debbie Moon at 2012-07-02 17:31:07:
To get things started - here's how the coins are different. Chigurh's coin is all about randomness from the beginning. It's an ordinary coin that's made special by the role it plays - determining whether someone lives or does.
Harvey's coin is special from the beginning; it's a symbol of his determination to control (for the best of reasons) what goes on in Gotham and in his life. He goes through the motions of making random decisions, but he knows the coin toss is fixed. Until the Joker shows him the "value" of true randomness - it's an abdication of responsibility, of control. Now Harvey not only doesn't have to control everything that happens, he can enjoy being 'out of control'.
Actually, I'm not sure what I'm saying here! :) But there's something in there...