If you have all one and none of the other you ain't ****. You don't need both in spades, necessarily, but to achieve even a modicum of success you need to have enough of whichever one you have less of....average or better.
Heart to me is more important. In boxing u will come up against more skillful fighters its ur heart that pulls u through. To be a great champ u need real heart and grit.
Then Juan Ruiz (facing Gary Russell Jr. tonight) would be champion by now. He possesses more heart and grit, and has a better chin pound for pound, than anyone in the sport. Literally anyone. I defy you to watch a fair amount of him and find someone who exhibits more of any of those qualities. You won't. Skills (and natural talent, which is different) pay the bills. Skills, heart, and talent = the makings of greatness.
Skills can only take you so far without a ticker. When there's nothing left in the tank, the guy with the biggest heart will out-gut the better boxer.
To be a champion you need both.. Of the two though I prefer a fighter with guts & balls of steel like Arturo Gatti, or Antonio Margarito over highly skilled cherry pickers like Mayweather jr, Jones jr or Joe Calzaghe
Neither is more important than PED's. Without the PED's you have nothing. PED's, PED's, peds, peeds, pds, PEDS, Peds.
Too bad that Mayweather has the cojones of a gnat isn't it. Floyd is a punk , a woman beating street punk, who happened to be blessed with incredible boxing talent. Basically he's wasted that talent. Just imagine if he had a set of balls like Margarito or Gatti. THEN & only then would he be regarded as an ATG