So, I actually bought a new series 8 SS w/ cellular just 2-3 weeks before the series 10 was released. I used the S8 for those 2 weeks, it was a great deal from walmart, and this new watch had 100% battery health when checked in settings. I decided to instead get the series 10 given the bigger screen (I was coming from 2 years use of the ultra which had just been too bulky and in-elegant for me). And now having the series 10 vs the series 8 just a couple weeks ago, I noticed a noticeable battery difference. Whereas I was ending my 7:30A - 11P days usually with 20% or so battery life on that new S8, I now see around 30-40% battery left on the S10 by that same 11P sleep time. Same usage, with cellular and AOD enabled, and occasional Gym sessions 3 days or so out of the week. So yes, while not "multiday" battery life like the ultra, my new S10 for me seems to be much better battery wise for comfortable 1-day use compared to a new series 8.
That experience alone, made the S10 worth it and I returned the S8 within the 30d return window. Hope this helps.