I haven't been able to look into the video spec but it's a different CPU in terms of driving software as well. So it's quite possible there's less difference in picture than there is in performance.
Seemed the same to me certainly didn’t seem any slower loading Netflix, Prime etc. Xbox One X with HDR looked as good as mine after I tweaked the settings. The settings I used are very similar to mine too.
Tbh I’m sure most of the added improvements are just marketing to make you spend more. If I had seen a B9 sooner I would not have paid the extra for my C9 but when I was looking the B9 was not widely available. Surely not a sales tactic....lol