where to put .button() call

When using a jQueryUI button in a datatable, it seems that either of these works:

"fnRowCallback": function (nRow, aData, iDisplayIndex, iDisplayIndexFull) {
  $(nRow).find(".the-button").button({ icons: { primary: "ui-icon-cart"} });
  return nRow;
}

or

"fnDrawCallback": function( oSettings ) {
       $(".the-button").button({ icons: { primary: "ui-icon-cart"} });
}

Is one preferred to the other? Am I going to run into problems with these approaches?

Thanks,

g.