AirPods definitely have significant latency on iPhones. (I'd estimate at least 100ms.) Perfectly fine for movies or podcasts, detrimental for calls, and awful for anything gaming related.
They don't seem worse on the Pixel 4a, but they definitely don't seem better.
“AirPods Pro and Powerbeats Pro that are wirelessly connected to an iOS device, such as an iPhone 11 or iPad Pro, should have very little, if any, latency in audio with respect to the visuals on the screen.”
AirPods and AirPods Pro in my phone or laptop (linux) both have no noticeable latency.
My wife and I pair both our AirPods pro at the same time to the Apple TV to watch shows (daughter sleeps in the same room) and never have any latency issues.
That's because the video is delayed as well, to match the audio latency. AirPods switch between Headset Profile HSP) (low latency, mono, best for voice) and Advanced Audio Distribution Profile (A2DP) (high latency, stereo, good for music) to accommodate both use-cases.
They don't seem worse on the Pixel 4a, but they definitely don't seem better.