Both really great skaters, though I voted for Kwan.
Yu-na produced easily the best Olympic ladies' FP in recent history. That program was phenomenal, technically and artistically. However, obviously, she didn't deliver often enough. Only in 2009 and 2010 did she win major titles and didn't make any major errors that would have prevented her from winning. In the other years, she either messed up the short or free. And while she is artistically a strong skater, her programs don't stack up to Kwan's. Giselle and Arirang in 2011 could've if she skated to her full potential.
I don't get why everyone is bashing Michelle for her lower technical ability. Michelle may not have done difficult combos like Irina or Tara, but her technical ability was nothing to be scoffed off about. Keep in mind that during her time, it wasn't the norm for most skaters to be attempting difficult triple-triples. Looking at her rivals throughout the championships - Chen, Butyrskaya, and Cohen generally didn't land triple-triples against her. Lipinski consistently did a 3r-3r. Slutskaya only landed difficult triple-triples in some of her programs, and often wasn't successful. I wouldn't count Hughes in, because she generally was not a rival. Arakawa landed a triple-triple-double in 2004, but otherwise didn't land the triple-triples all that often in major competition either.
Kwan's 1998 LP at Nationals is so far ahead artistically of everyone else, it more than compensates for her lack of triple-triples.
If Yu-na wins a couple more major titles, than I'd consider having her win such a competition.