I usually keep my iPhone 7 Plus in my messenger bag, which is slung over my back. So the signal has to go through my bag and my back and I never experience drop outs.
It could be that the 7 Plus simply has more powerful BT radios, of course. Or maybe I'm more radio transparent. Or maybe you walk in either areas that are extremely open (no surfaces for the BT radio signals to bounce off of), or where radio interference is far greater.
Could be a lot of things. Even the Airpods, of course.
I just tried connecting them to my back-up iPhone 5S and the BT radio seems to be stronger on that device when compared to my iPhone 6. Will try using the 5S when I'm walking to work on Monday (that's when I notice it the most).
My AirPods cuts out when I walk past the security checkpoint at wotk...
Which phone do you have? When I walk around the Oculus near WTC in New York, the signal cuts in and out like crazy. Most likely all of the commuters.