If you're gonna only use Linux, then the 9070 XT.
If you're gonna be on Windows, or will be switching to Linux 1-2 years later, or care about the NVIDIA software features, go with the 5070 Ti. AFAIK there's a bug with the open source NVIDIA drivers for Linux that causes the decreased performance on Windows vs Linux. Once that is fixed, the performance should be around the same or better on Linux.
The AMD card will outperform the NVIDIA one (on average), but NVIDIA's software features and innovative capabilities are superior to AMD's, and the cards are just more versatile for that reason. However, if you don't care about any of that and just want raw performance the AMD card will be better.