The only differences on the 64GB and 256GB models compared to the 512GB model are that the screen doesn’t have the anti-glare etching and you don’t get as nice of a case. Also you don’t get some software perks like special keyboard styles.
If I used my Deck more than I actually do, I'd genuinely consider getting the 256GB model and upgrading the storage, just to get the glossy screen.
Here is a blog post that shows the differences most realistically to my perception of it.
It's not like Deck has a great DPI or brightness to begin with, but the matte coating makes it even worse.
See the "text clarity" and colors comparisons of what the coating does to displays here: https://tftcentral.co.uk/articles/eve-glossy