I had a Galaxy Watch with an S10 and there simply wasn’t the same amount of thought put into the software on the Galaxy Watch.
Here’s a good example: Music playback. On the Apple Watch I can look at my wrist while music is playing to see what’s playing (I don’t always know who the artist is because I download lots of suggestions), adjust the volume, like/dislike a song by going one tap deeper, very quickly. The time stays on the screen so I can still tell the time all the time.
With the Galaxy Watch, I had to go two taps in from the now playing screen to adjust the volume and then back to see what was playing, and there was no way of telling the time without leaving the now playing screen.
They seem like small things, but the Apple Watch makes these small interactions easy and intuitive in a way the Galaxy Watch doesn’t.