Choose by your phone. iPhone: the AirTag (2nd generation). Samsung Galaxy: the Galaxy SmartTag2. Any other Android, or a family with both: the Chipolo POP. They all find a bag the same basic way, by borrowing millions of nearby phones, so the network your phone belongs to matters more than any spec.
Why your phone decides it
A tracker has no GPS or SIM. It sends a small Bluetooth signal, and any phone on the same network that passes by reports its location. In a busy airport that's thousands of phones an hour. The AirTag uses Apple's Find My network (every iPhone). The SmartTag2 uses Samsung's network of Galaxy phones and works only with a Galaxy. The Chipolo POP works with either Apple's Find My or Google's Find Hub, but only one at a time, which is how it suits an Android phone that isn't a Samsung.
At the carousel: finding the exact bag
The AirTag and SmartTag2 have ultra-wideband, which points you to the tag with an arrow and a distance when you're close. Apple says the second-generation AirTag does this from 1.5 times farther than the original, with a speaker up to 50% louder, useful in a pile of identical black suitcases. The Chipolo POP has no ultra-wideband, but at 120 decibels it's the loudest of the three.
When the airline loses it
This is the AirTag's big advantage. Apple's "Share Item Location" sends the airline a link to your bag's location, and Air Canada, WestJet and Porter accept it with a delayed-bag report. With the others, you can still show the agent the map on your phone. Either way, file the report at the airport before you leave and keep the file number.
Batteries and weather
The AirTag and Chipolo both run on a CR2032 coin cell for about a year, which you swap yourself. Samsung quotes up to 500 days for the SmartTag2, or 700 in power-saving mode. The AirTag and SmartTag2 are rated IP67 (dust-tight and fine if dunked), the Chipolo IP55 (rain and splashes), which is plenty inside a suitcase. All three are allowed in checked bags: ICAO lets devices with less than 0.3 g of lithium metal stay on in the hold, and a coin cell is well under that.
Attaching it
The SmartTag2 and Chipolo have a hole for a keyring or luggage strap. The AirTag doesn't, so it needs a holder. Wherever it goes, put it inside the bag, in a zip pocket, not clipped to the handle where it's easy to pull off.
Our full luggage tracker guide, and what to do when a bag doesn't arrive →