Pretty evenly matches cards overall. If you were talking about the 2080Ti, then that would be another story.
The 1080Ti has the advantage of extra VRAM. The 2080 has the advantage of RTX and DLSS, but less VRAM. When it comes to rasterizing performance, they perform pretty evenly for the most part within a few percent of each other in terms of raw fps.
If they’re the same price, I would choose the 2080 because it’s newer and has more features (better future proofing). But really, either one would work fine.