sardonic versus sarcastic

Well, here is an explanation of the differences amongst sarcastic, sardonic, and related words:

Sarcastic
1: a sharp and often satirical or ironic utterance designed to cut or give pain <tired of continual sarcasms>
2: a mode of satirical wit depending for its effect on bitter, caustic, and often ironic language that is usually directed against an individual b : the use or language of sarcasm

Sardonic - disdainfully or skeptically humorous : derisively mocking <his sardonic expression>

synonyms - SARCASTIC...SARDONIC mean marked by bitterness and a power or will to cut or sting. SARCASTIC implies an intentional inflicting of pain by deriding, taunting, or ridiculing <a critic famous mainly for his sarcastic remarks>... SARDONIC implies scorn, mockery, or derision that is manifested by either verbal or facial expression <surveyed the scene with a sardonic smile>.

Looking over Phoenix32890's post and comparing it to the definitions I found from Merriam-Webster Online, I'm starting to see a subtle difference that may be along the lines of wanting a reaction or just making a statement. Sarcastic seems to want a reaction. Sardonic seems to be making a statement.

In my personal usage, which of course may be particular to me, I use sarcastic and sardonic slightly differently. I think sarcastic is a bit more raw, with a bitter tinge to it, a shade of defensiveness in it. Sardonic I see in a more positive way, more as wry aside, not as much the words of alienation. The sardonic comment would leave room for the subject of the comment to fit into the world's scheme somehow.