After testing some more and playing a few games and really paying attention to the Bluetooth delay factor, sorry to say that I have found the Bluetooth audio delay to be abysmal for the Spirit Pro.
Here are the approximate delay times (on iOS, using an iPad mini 4 and iPhone 5s; the elapsed time when a key is pressed on the virtual keyboard until when the sound is heard) for all of the wireless Bluetooth headphones I have:
Anker Soundbuds Slim +: ~.5 second
Anker Soundcore Spirit X: ~.25 second (negligible)
Anker Soundcore Spirit Pro: ~1.5 seconds (!)
If you'll just be listening to music with the Spirit Pro, they are fine. If you'll be playing games or videos where audio sync is important, maybe look elsewhere.
Note that I tried multiple times to delete the pairing to all devices, reset Bluetooth on the headphones (connect to charger, press and hold "+" together with ">") to get the delay to be tolerable but nothing I did would diminish the delay.
Just telling it like it is...no sugar coating.