Same, image quality with DLSS on was a vast improvement even at 4K. 62fps at 4K with 2x 2080 Ti's vs 34fps with DLSS off
http://www.3dmark.com/nd/30058
I think what some people are seeing as image improvement is in part down to the higher fps with DLSS.
This is something I notice with the ordinary Port Royal without using DLSS when comparing a single card to SLI.
Having said that when using SLI it is hard to tell when DLSS is off or on when looking at image quality as the fps are quite good (85fps v 120fps).