Both are being used, they just come from different suppliers. You could get either. As I understand it, if the serial number has an "A", you get the top version. If a "B", you get the bottom.
Apparently they cost about the same but do have different characteristics. For example, Dr. Turbo has said that "B" has better torsion strength.
"Both prepreg tube and filament winding tube meets the standard of inspire 1 so they will not bring in any noticable performance difference. As a matter of fact two tubes cost almost the same. DJI chooses to use them both simply to secure the supply chain."
I had a Type A to begin with (had to RMA due to a camera lens fault) and it was replaced with a Type B.
I've flown about 4-6 good flights on each and there is no difference between the two types. They felt exactly the same.I would however prefer the Type A though as it looks cleaner and has the same weave as my other multirotors.