Both plugins do track, however, the way that they track is different. FCPX Auto Tracker 2.1 is best for tracking single points or an object such as a football and FCPX Auto Tracker Perspective 2.1 tracks the location of 4 points and is best for tracking planar surfaces such as a brick wall.
The track editors are similar, however, they do have a few different control options such as the Tracking Type. In FCPX Auto Tracker you have the option of using Position Only, Position + Scale, Position + Rotation, and Position + Scale + Rotation.

In Auto Tracker Perspective you can instead choose from two different methods of tracking: Planar and Corner Pin.
The Planar tracking option will track the details inside the plane selection.

The Corner Pin option will track the corners specifically and not the details inside the larger plane.

Only FCPX Auto Tracker 2.1 has an option for text, though you can always put a clip of text in the drop zone in FCPX Auto Tracker Perspective 2.1.
You will have to determine which tracker will be more relevant to what you are trying to accomplish.
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FCPX Auto Tracker 2.1 will work best for tracking text or media to follow a subject while it moves across the screen.

Learn more about FCPX Auto Tracker 2.1 on the store page below!
https://store.pixelfilmstudios.com/product/fcpx-auto-tracker/
More tutorials for Auto Tracker 2.0
Daniel Schiffer
https://www.youtube.com/watch?v=XJuh1Zq3Spg
KingTutsPro
https://www.youtube.com/watch?time_continue=1&v=Vl_hls2Ep5w&feature=emb_title
Jeven Dovey
https://www.youtube.com/watch?v=Rf4wmBp7RMQ
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FCPX Auto Tracker Perspective 2.1 will be best for tracking media to a surface such as a green screen on a phone or a billboard or any other surface where the media needs to change perspective with the environment.

Learn more about FCPX Auto Tracker Perspective 2.1 below!
https://store.pixelfilmstudios.com/product/fcpx-auto-tracker-perspective/
More Tutorials for FCPX Auto Tracker Perspective 2.1
Emilio Takas
https://www.youtube.com/watch?v=4ScgKB_ixcA
Serge M.
https://www.youtube.com/watch?v=LkwgL_ECcaE