So if SpaceX needs video of the landing/crash sites then you could buy a few drones instead of a single dog. Because of possible debris and fire on the ground I also expect a drone would be better, and if teh land is clear then a drone could also be configured to land and film from the ground(because you could afford multiple ones you can have different configurations).

I might be missing something though, a scenario where an robot with legs can do better then a flying or wheeled one.

Fires, especially large hots ones, create wind and other aerodynamic instability.