Here is my TLDR post.
I like to use them all to complement each other - the AP, my eyes, KenPom (don't use Sagarin), and the RPI because its a necessary evil. To me the deeper you want to rank/follow feams outside of the top 10 in the country the more you need to rely on something like KP.
How many of us actually watch every team (or at least the top 75 teams) enough to from judgments on how they should be ranked, or at least what level that team is at? Nobody here. We can rank top 5 / top 10 based on what we have seen and results early on fairly well. But after that?
Lets get the semi garbage out of the way first - RPI. Its an awful ranking system, technically unsound, yet obviously relevant due to tournament implications. For Syracuse less so, but if you want to understand what conferences are lining up well for tourney seeds the RPI is extremely important in November and December. I am not looking at who is #1 in RPI, but what conferences are doing really well. The amusing thing is that conferences can game or just luck their way into better RPI rankings - it doesn't matter that the RPI stinks, the RPI matters (especially for tourney level teams not expecting top seeds)
The AP Poll / Eyes: Not necessarily the same, but I group them together because they have similar limitations. As I mentioned before you cant see them all. But at the same time most are able to focus and see the results of the top teams. We can come up with a logical top 5/top 10 with some viewing and some simple comp of records. We can come up with arguments who is #1 or #2, or top 10. Especially by this time of year, the teams with 0-1-2 losses are thinning out. But the rankings are often impacted by pre-season ranking - some good teams play no tough road games, while others play more. A factor not adequately captured in AP Polls, esepcialy as we move further from #5.
But will your eyes tell you who should be in the top 20? Top 30? Top 40? Do you trust the AP fully in these ranges with all their biases? Teams change a lot from year to year, and we don't see enough of most of them. Our observations are typically based on prior years - we have nothing else to go on. But teams can change a lot quickly in the NCAA.
So to me this is where KenPom came in, especially at this time of year. I think a lot of people struggle with KenPom because its not based on W/L. Its basically based on how many points you score and allow per possession adjusted to schedule.
For example. one 4 point loss vs a 4 point win will not change your KP ranking much. After all its 8 points over the course of all your possessions. But in the eyes of AP rankers (and in my vote if I had one), and especially when we are discussing the top 10 today, that decision (win or loss) has a huge impact on your ranking, and rightly so. KP does not rank top teams in the way we have been framed to evaluate the top 5/top 10 teams in America. It doesn't mean its flawed - the difference between a number 1 and number 5 team is typically minute, and the ranking system is meant to rank 350 teams not 10 teams.
How do you evaluate your more middle of the pack teams? There are a tonne of teams that are 8-3, 7-4, 9-3 for example, but givens schedules, there can be big difference in those teams. How do you know (or try to understand) what teams are in line for the tourney, before the conference season actually starts. How do you determine who may be underachievers without relying on prior observations/biases? Well the AP and eyes wont really help you past #15 IMO. So this is where a good ranking system comes in that has no biases.
Many of you don't really care beyond this level which is fine - teams outside of #15 are not the competitors of Syracuse at a national level. But how can you make blanket statements that Clemson sucks for example. None of us have seen enough of the middle of the pack.
Do I think Syracuse/Arizona or Louisville is #1? Syracuse/Arizona should be #1. Either way the cream has risen to the top in the poll or the KP system. But I would also argue that teams that are ranked way more higher in AP than KP, are the teams that are likely going to fade (for example Storrs) I am sure if KP was an AP voter his rankings would not be the same - he would also consider a close W or L more than his system. He would also say his rankings are not meant to be a full basis for his AP vote.
In order to adequately rank teams outside of the top 15 and to rank 350 teams, you need such a margin / efficiency based systems. W/L are not possible or you end up with ridiculous garbage like the RPI.