I love my Tab s6. Great little device. Use it every day.
I bought the Tab s8 Ultra with keyboard case. after its release. Gorgeous tablet but too darn heavy for me to use anywhere but sitting at my desk, which is where my PC is. I don't need a tablet at my desk, so it doesn't get used much. (Oh also works on the treadmill. Again, not much usage.

) Bad call on my part. If I had to do it all over again, I would get the s8+.
So I think you're wise in going with the plus model if you feel the Ultra series is too heavy.
Samsung is slated to end security updates for the Tab s6 this year, if I remember correctly. This is probably a good time to trade it in! $250 sounds pretty good.