I appreciate that you can see the positives in both runners, however I think you are misjudging the times.
This season, Josh Kerr has run 3:27.79 3:28.64 (Converted from Bowerman Mile), 3:31.46, and a road mile that converts to around a 3:47 mile or basically another 3:31
Jakob for 1500m has run 3:26.73, 3:27.83, 3:28.24, 3:28.88 (Converted from Bowerman Mile), 3:29.52, 3:29.74, and 3:31.95. (has one more race, not sure how fast he will go)
So it is not really a tie when the converted 1500m times from the mile still show that Jakob has run the fastest over many races over 1500m. Just because someone is a world leader in an extremely similar event does not make it a tie.
If we even compare 2 mile/3k times, Josh Kerr has run 8:00.67 over 2 miles which converts to around 7:25 for 3000m.
Jakob has run 7:17 which is almost 8 seconds faster. So, in the department of PBs and fast times, Jakob is the fastest and most consistent runner over Kerr and it is not really that close.
I'm not sure why the Euro 1500m does not mean much? If we are comparing fields...the 5th avenue mile field was also watered down with only Hobbs Kessler and Neil Gourley as runners who were finalists from the Olympic 1500m final. The European 1500m final also had Olympic 1500m finalists in Neil Gourley and Pietro Arese as well as other Olympians as well, these two races are effectively the same and we can cancel them out. Kerr's 800m doesn't really add into the conversation since he only really ran 1:45.94. That is only half a second faster than Ingebrigtsens PB and almost 6 seconds slower than what any of the true 800m men have run as well. Distances from 1500m-2mile are more apt for comparison and a time in the 800m does not negative a European 1500m final.
I agree we can cancel out Pre and Zurich. Lausanne is absolutely not inferior to Kerr's road mile. Like I said above it was (1) A watered down field, and (2) in a time that is alright (3:30-3:31) but not comparable to 3:27.83. Just because the course record is extremely old does not make it this insane extraordinary performance. The only men of note to give Maree's record a shot were Peter Elliot, Steve Scott, John Walker, and Bernard Lagat. Imagine if El Guerrouj? Cram? Or Coe gave it a shot? Let's not forget that Lausanne is also an old meeting that was apart of the old five IAAF Super Grand Prix meetings. So, I would argue that it is more impressive that Ingebrigtsen was also able to break a meeting record in 3:27.83 despite being run in the past by all time greats.
I agree with you that only 3.5 months of racing is hard to sell to someone as Middle Distance athlete of the year but that is why I am here trying to convince you ;)
I will concede that Jakob has had three significant losses with one of those being the Olympic Final, Pre, and Zurich. He has won no medals from the WIC or Olympics in Middle Distance events.
If we look at Kerr, he lost very badly in Zurich and that loss was even worse than Jakob's since he placed 5th instead of 2nd and was almost 2 seconds behind (losing to Laros who is 19 years old). Kerr was also beat to the gold in Paris and only beat Ingebrigtsen by a half second, not very dominant and perfect from Kerr either.
To me, Jakob's fast times and consistency trump Kerr based on the analysis from above, feel free to disagree and I suspect you will. Good day!