iOS Bluetooth Weirdness

Since receiving my fabulous new Philips M1BT headphones for Christmas, I've been listening to a lot more audio. Mostly music, but also audio books, podcasts and Instapaper articles via VoiceDream.

I've noticed that there are some odd differences in Bluetooth performance between the iPhone 5S and the iPad Mini Retina. On the Mini, it seems to work flawlessly with any of my Bluetooth audio devices. Good quality, no dropouts.

On the 5S, it seems to work perfectly with the default Music app, but on any spoken word audio, it'll quite often miss the first few words of a sentence. This also seems to happen with music streaming apps, such as (whether actually streaming, or playing back downloaded content). This seems more noticeable with the M1BT's (which work perfectly on the Mini using the same spoken word audio on the same app), but is still apparent, although less noticeable, with other Bluetooth audio devices.

It's almost like it's trying to buffer, but missing the first 2-3 seconds. 

Anyone else come across this? I've tried all of the usual resetting of Network settings, rebooting the phone, un-pairing, then re-pairing.