I'd still stick with a Ball for range of motion and if real precision is necessary, a macro rail will give better control and range than either of these by themselves.......
Macro rails only provides precision in two directions. Geared heads provide the same level of precision as macro rails in 3 dimensions, none of which the rails cover.
If you are even bringing up pan/tilt/swivel heads then you clearly have no idea how a geared head works. A geared head is just that, a head that adjusts using the accuracy of gears. You turn a knob, which turns gears, which turns your camera in the associated direction. There are three knobs on a Manfrotto 400, 405, and 410. Each one adjust the camera in a different direction in smooth less-than-one-degree increments. The each also have a lock-release so you can make rapid movements to get "close" to where you want to be quickly, then finish off with the fine adjustments.
The first knob turns the lens left or right up to 360 degrees.
The second knob tilts the head up to 30 degrees left or 90 right.
The final knob tilts the head upwards up to 30 degrees and downwards up to 90 degrees.
Combine the geared head with a macro rail and you have ultra-precise control of:
Left/Right Facing. Upwards/Downwards Tilt. Left/right Tilt. (gaered head)
Forwards/backwards Movement. Left/Right Movement. (macro rail)
Throw in a geared tripod and you have precise control of the only missing dimension, Upwards/Downwards Movement.
In comparison to a pan/tilt, ball head, or even Gimbal head..... well there is no comparison. None of these come even close to the same precision. Even that giant Arca pictured earlier can't hope to be even half as precise as a geared head.
Anything where fast movement is not needed but precision could be useful. So things like: Macro, Astronomy, Super-long telephoto of precise locations, Landscape, Product, Portrait, Panoramas, Architecture, etc.
A real life example would be when I went to shoot an eagle and baby-eagle in their nest recently. I ended up at 1344mm effective focal length doing manual focusing via 5x live-view. Being able to make the most minute of adjustments to where my camera was pointing was invaluable. I was able to center dead on the eagles head and keep its head in frame even when it moved around a little, so I could precisely adjust focus for the eye at all times.



Hope to see some results
