Having run SLI for just over a decade i fully agree with this, i would never go dual card again either SLI or CF.....
Two GPU is most definitely not better then one.
Maybe if your crypto mining...
Maybe if they scaled 100% actually give me even 33% scaling and i wouldnt complain as much, but it doesnt.
Nvidia has the worst driver support for SLI.
Infact its gotten worse then it used to be with the older gen cards when you could manually set the cards to render.
(render 1 and render 2)
SLI causes micro shuttering, as well.
I can go on and on about how much fail SLI is, and this is coming from a person who used to SLI/Xfire in all my builds.
So sorry to tell you this but, a Single 1080 Ti >>>>>>>>> 2 x 1080 GTX.
Because that Ti has more ram, will most likely run flawlessly with any game that comes out on 0 day, with minimal driver support.
Also you wont be at the mercy of Nvidia's lazy driver department rolling out SLI drivers for a game which most likely you would be done playing with.