I think neither is suitable for QT designers. Qt prefers photoshop files and does not have Xd integration yet. I would try Sketch web because it works well with QT designers.

If you like to use most popular software than you need to use XD.

You can convert XD files to psd using https://www.photopea.com

Qt Designers can import UI design files from Adobe Photoshop, Sketch, Maya, MODO, or Blender to Qt Design Studio, which can turn them into code for your developers.

You can export your Adobe XD into SVG (Scalable Vector Graphics) format but it does not help for QT designers.