I received my Apple Watch Series 8 today, upgrading from the 6. People say it's almost no difference, which I largely agree with. However one subtle difference for me is the better readability on the newer model, which I believe is only 1 mm bigger. The spacing of small text and numbers in the weather app, for example, is much better on this newer watch, even when both updated to the latest watch OS. It is a series of small UI tweaks that make a noticeable difference for me, when interacting with the watch. And even if battery life is roughly the same, the battery on the 6 was not holding up well after two years of use.