As for 5 seed versus 4 seed. I think USUALLY being a 4 is better, but I can contrive scenarios where being a 5 is arguably better. It's not that hard the way things are constructed today.
But I don't think you can really tease out the structure of the playoff and the understanding of exactly who that 5 seed might be.
That 5 seed might be squarely in the discussion of the #1 or #2 team in the country. Think of 2011 Alabama. Smoked literally everyone on their schedule except LSU, to whom they lost in a
very narrow OT game. So close that despite the H2H loss, they ended up in the BCSCG.
They were not the #5 team in the country, but in this scenario they'd assuredly be the #5 seed. I could argue that facing the weakest P4 conf champ and the strongest G5 conference champ is an easier path to the semis than facing the #7 seed in the CFP (which arguably could also truly be a top 4/5 team in the country who just didn't win their conference). There's a good chance those two teams they face could be outside the top 10, when actual talent and rankings are considered.
And then you have to think about who that #4 seed would be in our structure. Most years, it will be the weakest P4 conference champion. It's tough to look back at 2011 as an example here, because we still had 6 power conferences, but it is still instructive because 3-4 of their conference champs were fairly weak. Sure, LSU and OkSU were locks. But who comes next?
You had #6 Oregon at 11-2 (behind #4 Stanford who didn't win the conference). You had #8 Boise State (11-1) who wasn't even P6 champ next up. Then #9 Wisconsin (11-2). Then #14 Clemson (11-2). Finally #23 WVU (9-3).
If we take the rankings at face value with the top 5 conference champs, you'd get the below CFP seeding:
- LSU
- Oklahoma State
- Oregon
- Boise State
- Alabama
- Stanford
- Arkansas (slots in where USC would be as they were ineligible)
- Wisconsin
- USCe
- KSU
- MSU
- Michigan
- Clemson
- Baylor
So completely ignoring structure, if I'm Boise State, I don't really want to be the 4 here and face Alabama. But as the 4, I can at least hope that somehow Baylor upsets Alabama, or Alabama loses key players to injury, or something else. If Boise and Alabama swap, then Boise has to first of all beat Baylor, and then they're guaranteed to face a healthy & rested Alabama.
I think the point stands. Even with the extra game, the team that will most likely be in the 5 seed position is going to have just about the best possible path to the quarterfinals of any seed in the playoff.