I currently have a Nikon D90 with a Nikkor DX AF-S 35mm f/1.8G and Tamron 18-270mm F/3.5-6.3 DI II.

If I was to upgrade to a mirrorless, and had a small budget, should I go with the Nikon Z6 and an adaptor to keep my lens, or should I go with something else like Sony which, from my understanding, have great eye focusing abilities?