85" 8K
I imagine, if you get the one with lower price, you can save more $$ for a very good and high quality home theater system, I imagine a good brand of home theater could be better than the integrated audio of the screen.
Why the difference of prices?
some new features including "alexa" , more "power of processing with its chip",
not a wide difference to worth the upgrade I think. I've seen (on youtube) fantastic 4K TV rooms - of course an 8K setup would be excellent, considering the prices like that, you could include smart lights and amazing sound and I bet with lower price.
even if you have enough budget $$$ to get the more expensive and best audio system, it would not be smart purchase/setup, wasting some features.
4K is enough to me - considering the kind of media I display and the TV provider