Re: Does the best chin always beat the biggest punch?
Nope. Sometimes it does, sometimes, especially if the guy with the great chin doesn't have much else going for him, it doesn't.
See Mosley-Margarito for example. Margarito was a slow target who kept walking into Mosley's shots while being unable to do effective damage himself and being unable to adjust to what Mosley was doing. End result was Margarito being KO'd.
On the other hand you have cases like Julian Jackson vs Thomas Tate. Tate had a good chin (one career stoppage, that being against Roy Jones Jr where Tate walked into a left hook and was wobbly afterward, although the speed of Jones probably troubled him more than anything) but more than that he could fight defensively, jab, counter Jackson's jab with a decent right hand. The result was that Tate could take a lot of what Jackson dished out, and he could minimize the effectiveness of it.
Of course, there are a few guys who are freaks and nearly impossible to KO, at least at the weights where they fought in their prime. For example, see Wayne McCullough, Chavez Sr and Marvin Hagler.