Before my current S6 Apple Watch, I owned an S2 and I remember how slow it got after a couple of WatchOS updates. So, I had a bad experience with the WatchOS software.
On the other hand, my S6 has a new SoC and it flies through typical tasks. I hope it stays that way.
With every update for the WatchOS and iOS, my devices have gotten slower. That might be due to weaker batteries, new processor-demanding software features, or simply unoptimized software from Apple. Whatever it is, I feel my devices should feel much slower after each update.
Thank you for writing your experience with your iPhones and Apple Watch. I think my environment and internet connection played massive role in my experience with Apple products.