How do you decide who the best 4 teams are other than the results of the games played?
A 12 game season without a lot of crossover and with home field advantage being a big thing is not going to allow you to determine the 4 best teams based off of overall record. Usually there is going to be a clear line somewhere, maybe between the best team and the next three best teams, maybe the top two teams look similar and then there is a drop to get to the next four teams, or whatever combination.
Last year, I think there wasn't a lot of separation between at least the top 5 teams, and possibly not between the top 6 although there's not a strong objective case that FSU belonged with the other five. UGA, Bama, Texas, WSU and Michigan were clearly all close enough that any of them could have probably lost to any other one on any given night.
I would probably agree with the committee that FSU wasn't one of the four best teams, but again, you can't really prove it and I think that's why you should go off most deserving resume first, then use who is best as a tie breaker. Last year, FSU went undefeated against a weak ACC but they scheduled two SEC schools OOC that are traditionally good teams. I don't think you can penalize them when they voluntarily scheduled LSU while also having UF on the schedule. They should have been a shoe in with Michigan. After that, I think UW also deserves to be in. Their OOC was Boise St, Tulsa, and the other MSU. That's not a great OOC schedule, but they have 9 conference games and schedule one out of 3 OOC against a decent Big10 school, and the two G5 schools are respectable G5 schools. I think that's enough.
At that point, you can toss a coin between UGA, Bama, and UTexas. None of them could really complain about getting left out, but each of them could complain about getting left out over another team. If you want to go off of best win, UT at Bama or Bama against UGA give you the best win. If you want to go off of least bad loss, it's UGA then Bama. UGA has a case that they are the only school that made it undefeated in the regular season and shouldn't be penalized for a championship game when the resumes are that close. But I think if somebody plays in a more or less big boy conference and at least makes an effort to schedule decent OOC competition, I don't think you can penalized an undefeated team because you think a one loss team is better.
Somewhat off topic, if you go by most deserving resume, OSU loses one of their championships because while they were the best team at the end of the year, they had a bad loss (I think to like a 6-6 Va tech team?) that made their resume undeserving of a spot in the playoffs.