Question about MSI GeForce RTX 2080S GAMING X TRIO

Salute

I think it all depends on whether you want/need to use ray tracing. When comparing some benchmarks, it is noticeable that the 2080S and the 1080ti models are pretty much on par. The difference is that you can't use ray tracing with the 1080ti.
If you really want more performance in general (e.g. more fps at 4K), you should go for the 2080ti. If I may give my personal opinion: I wouldn't upgrade if I were you. The 2080ti is not value for money and you won't really get better gaming performance with the 2080S. It will be quite some time before the gaming industry implements RTX "on a large scale", and until then new models will certainly come onto the market soon. Besides, RTX technology is still in its infancy. I can also imagine that RTX will never really become big (I hope not, since I own a 2080S myself and am quite satisfied).

Well, the MSI GeForce RTX 2080S GAMING X TRIO is a great card that also offers you a bit more FPS.
However, it "only" has 8GB - so you're taking a step backwards.
All in all, an upgrade does not seem compelling to me (yet).