My reasoning/logic for picking the B9 vs the C9.
1. My current TV broke a month or so a go, I have not had a TV since then.
2. I am not a big audio/video phile, but its nice to know you have the "basic" stuff you need.
3. HDMI 2.1, 4K and HDR support was important to have.
C9 seems to be like the best one in regards to my requirements, but the pricing was a bit more than I wanted to spend on a TV ( I know I am getting old, when I was younger, there would be no such issues, if the tv was like THE tv)
B9 have HDMI 2.1, 4K and HDR, it does not support HDR+, but again looking at item #2, I will probably not notice much. And the B9 is decently future proof I think with HDMI 2.1
As for the A9 vs A7 gen 2, I was unable to find any solid info about how big of an impact it has or not. I assume the Smart AI stuff needs a beefier CPU, but I am not using the smart features and the TV is not even connected to my network. So only way it can send data on my usage is if the TV hacks my wifi or sends it over the HDMI connection through the STB or PS4Pro.
So if I was really pedantic, it is the lack of HDR+ that is my pet peeve, but being realistic, I probably wont miss in practice. Because I mostly can not see a difference I assume. And this assumption is based on the fact most of the times when I read stuff here on Beyond3D where people complain about image IQ etc, I am just WTF?!?!