S8 and S8+ are getting Android 10. As for iphone 5s yes it gets the update but not the full features unfortunately. Apple also tweaks the batteries software so the device can use the update at all. Updates from Samsung always come with full features and are not tweaked. Expect the update for the S8 lineup after the S10 and S9 get theirs. They go in order by newest to oldest, also the S7 will have a rom available to update to Android 10. The difference between Samsung and Apple is with a Samsung you can do anything; iPhone your just purchasing the name.
Sorry bro but the galaxy s8 will probably not be getting android 10. I had to part with my mine for my new note 10+. If it does I'm all for it but seeing Samsung's track record I think android 9 will be the final version for the s8.
Galaxy phones (may change for newer models in the future), receive 2 major OS upgrades, been that way for a long time, S8/Note8 shipped with Android 7, so Android 9 was it's last major update, they will not get Android 10 officially.