Under excellent lighting conditions, iPhone X will provide the better picture.
Under average/low lighting condiction improved optics + ISP on the 11 would provide a slightly better image with a 2x digital zoom vs iPhone X with 2x optical zoom.
On dark conditions, 11 is way better than X since it can't capture properly details in dark environment.
On average iPhone 11 camera is way better than X. X is good under perfect light and its 2x optical zoom is nice to have ofc ! but everything else is a step down from the 11 camera (Smart HDR, ISP, optics, night mode, selfie cam, main cam etc etc)