Benefit with different graphic card

Ok thanks! So basically I understand that the graphics would be very comparable if the quality is set to max in the apps? 

I'll happily make a better comment once my 'S' arrives - imminent, previous comment from original but still pretty relevant :)

On default settings, the image quality should be similar or the same (though some games will auto-adjust the graphics so 1080 Ti will look better). The bigger difference is that the 1080 Ti should run at full 80fps but 1660 Ti will probably be running at 40fps with smoothing. Honestly, I think this looks fine but some people have said it causes artifacts.

Nice, I think i would do the jump and drop 400 $ for the 1080TI

Actually, now that I am looking at it. A 1660 Ti would probably be fine. If you want to save the money it will probably still be a great experience (meeting recommended GPU). Obviously the 1080 Ti will be faster/better but you might not even notice a difference in many games.

yes
https://gpu.userbenchmark.com/Compare/Nvidia-GTX-1660-Ti-vs-Nvidia-GTX-1080-Ti/4037vs3918