Watches are 100% subjective to the user of course. I don't like either of them because they're too big for my wrists. The 45mm SE is more than enough.

Looking at the features though a Watch 4 owner could be looking at the new models and wondering whats new. And the honest answer is not a lot.

If you're happy with your current Ultra based on the glacial progress of the smartwatch industry I would say it should be good for another 4-5 years.