I use both of them.
The AirTag has only 1 very good feature and that's the "find my" network.
As I posted in another thread, the U1 chip is a joke, a gimmick. The precision finding only kicks in about 3 to 4 feet from the tag I'm looking for.
The Tile is seriously louder, almost 20 dB (at 1 meter). Living in a relative small house (2 floors) I can hear the Tile everywhere in my house. Not with the AirTag.
BT range of my Tile Pro is significantly better. Example: Keys (with AirTag) in my house. Myself standing in the garden, just a glass door in between. Distance in a straight line is appr. 25 feet. Searching for my airtag it's says "Weak signal", 10 feet more and the signal is lost ("searching for signal"). With a Tile pro I can double that distance.
With a Tile you don't need extra keyrings or holders!!
Tile has 2 serious flaws, the Tile "find my" network and the paid premium features and that's why I use them both.