Tbh I absolutely don't care if I get CBR or VBR as long as it looks good, so I will always prefer Amz over NF because of the bitrate and higher filesize.
I even prefer the way it is because I just click download, no need to think if I should get CBR or VBR. Still, I can understand that others wish to get it.
What I know however is that HEVC/ h265 is smaller while having the same quality (or higher quality while having the same size). Personally I don't need it either atm, but I would see it as a higher priority that the CBR/VBR thing.
Sure, it is smaller, but it is a newer codec so if you have an older device it might struggle in playing it. I even have problems to play the audio codec on a 4k Smart-TV that should be up to date, and since it can even play 4k I don't understand why it has struggle with the audio. (It was E-AC3 I think, but I am not sure).