It does bring some feature improvements year over year. Siri works offline on S9 and Ultra 2, the S10 has a neural network to remove background noise if you use it for phone calls.

Siri doesn’t really seem to work offline on my S9 despite the claims.

It's probably a limited subset of things that can be done on-device. Even starting a timer or workout doesn't work for you?

I have an S6 and if I go outside for a run without bringing my phone I definitely can't do it with Siri.

Good observation. I wonder if that's something S9 can do too.

Yeah screen brightness, viewing angles, being thinner.