There's HDR, HDR10 and the quality is not only that but the code and can be affected by the source video encoding. So HDR10 isn't going to help you with non-HDR10 content much.
Then you enter the tar pit where you compare one to another. For that I have to leave you with reviews. Use those reviews to compare.
I may not be asking this the correct way. I would like to know if the MU7000 HDR is quality HDR, or just more of a label. I read that not all HDR's are the same. That some are just more of a label. So I am trying to find out if the 7000 will make any real difference compared to 6400 (Ultra HD). I will be watching Hulu, Netflix, Sling. Not movies very much. The 7000 shows it has HDR. The 6400 only says it is only Ultra HD. That is what I am trying to get a grasp on. The more I read up on them, it gets more muddled.