This was discovered by musician, composer, and software developer Stephen Coyle where based on his tests, he discovered that the AirPods Pro has better Bluetooth latency. Using a metronome, Coyle found that with the original AirPods, which uses the W1 chipset, has a latency of 274ms.
For the second-gen AirPods which uses the newer H1 chipset, it has a slightly lower latency of 178ms, but for the AirPods Pro, Coyle found that it has an even lower latency of 144ms. This is almost half the latency of the original AirPods, although whether or not this is something that users will be able to pick up on is unclear.
That being said, it should be noted that this Bluetooth latency is more for measuring sounds that are considered “unpredictable”, such as user-initiated sounds, sound effects in games, and so on. According to Coyle, latency in videos can be easily addressed by delaying video playback, so this is not necessarily an issue.