Ok, I'll take back what I wrote above. I tried the measurement again and got 197ms round trip for the same 2nd gen AirPods and iPad Mini4 running current iOS. It's not the worst, but certainly not better than most of Bluetooth headphones. I'm not sure why I got the low number before and whether it was a measurement error or changed in a software update.
From what I am reading, the best of the Bluetooth headphones are claiming say 120 ms, and some have as high as 300 ms.
I just hope manufacturers keep making wired ones with active noise cancellation (ANC). Already it seems ANC is seen less often for wired ones than for the wireless ones.
My guess is that since ANC already needs DSP and small headphone amp, it doesn't cost much to add a Bluetooth receiver. Removing the cable input socket and ADC could even recover some of the cost. On the other hand, it seems that there's limited market for wired headphones right now.
