I own the Sony A7III and am very satisfied, but there are some points that speak for the Canon models.

1. the viewfinders on the Canon cameras are optical, so they have no delay. (Spotting advantage).
2. the DualPixel autofocus of the Canon cameras is the fastest AF system. (Spotting advantage)
3. then there is the question of whether you want a full-frame camera or an APS-C camera. Full frame would be better for landscape. Differences are explained here: https://martinkleinheinz.de/crop-oder-...

4. compare the prices of the lenses depending on your budget (full frame is more expensive and Sony telephoto lenses are very good but start at 1000+ francs).

5. SLR cameras have a longer battery life and the display on Canon cameras can be rotated and tilted. (Advantage for landscape photography)

6. Canon cameras can take more pictures per second in continuous shooting mode (advantage for planespotting).
7. Sony is more compact and lighter.

Conclusion: The 6D Mark II is the most suitable, but also has its price. For smaller budgets rather the 80D. The Sony has fewer advantages than the Canon models in this area of application.

If you have any questions, just get in touch again :)