I advocate for conference champions because it makes the conference race matter.
I think every team should have, as their first goal, winning their conference. If your second goal is winning the national championship, knowing that winning your conference is automatic entry to the second goal aligns everything.
Right now winning your conference doesn't matter. I mean, it does, because it's REALLY hard to get a CFP invite without winning a conference (although it's happened 3 times), but conversely 10 teams have won their conference and not gotten an invite. You can get into the CFP without it, and you can win it without going to the CFP. So winning your conference is neither necessary nor sufficient for CFP entry.
So for me, I want the conference champion to matter. Even if it means that "unworthy" teams might get into a playoff, it gives you a serious reward for winning your conference.