Which is better for tracking?
1080p60 will give better temporal resolution, which is key for tracking details that move within the scene.  If the scene is ridiculously simple, such as if the only object moving at all is a Mac screen on a swivel, and if you can control the speed of the swivel however you like, then framerate is no longer the sole determinant of temporal resolution.  You can achieve the same temporal resolution shooting a half-speed move at 30fps as you can a full-speed move at 60fps.  In that case, shooting at 4K will give you greater spatial resolution than 1080p.

In the normal case, temporal, not spatial, resolution is the big bug-a-boo for object tracking.