All about matchups.
If anything, UNC and to a lesser extent Duke, are the only ones that's really have had truly great runs in the tournament.
UNC makes it as an 8 seed, dominating Marquette, taking down 1 seed Baylor, and 4 seed UCLA to get there. Both were very good teams playing well at the time, even though both were also battling injuries to key players. But they just need to beat a 15 seed to make the Final Four...........
Duke took care of a 15 seed, beat a decidedly down Michigan State team, and then played like the ACC champ against an elite defensive team in Texas Tech. Now they get another good defensive squad in Arkansas that's playing its best basketball after everyone wrote them off as an upset special to Vermont.
Miami on the other hand got a lot of flawed teams on their path to the Elite 8, though to their credit, they are also playing their best basketball at the right time. They beat a good, but not as good as last year, USC team, a roller coaster Auburn team that wasn't going to win the title anyway because no team has ever failed to reach their conference tournament semies and gone on to win the national championship (so Auburn was a dead team walking regardless), and then a very offensively-challenged Iowa State team who also benefitted from their draw just to get to the Sweet 16..............But now Miami just has to beat top seed Kansas, who is looking more and more like a team that will unfortunately win the national championship.
So like I said.....it's all about matchups.