Apple Watch Ultra 3 vs Apple Watch Ultra 4: should you upgrade?

If you're buying new, get the Apple Watch Ultra 4. The Apple Watch Ultra 3 is no longer sold by Apple.

Brand new, with the longest battery life of any Apple Watch.

The Apple Watch Ultra 4 is 1 year newer, so it will get software updates for longer and holds its value better. If your Apple Watch Ultra 3 still works well, there's no rush, but don't buy one new.