In the U.S. at least, Motorola is a more recognisable/established than OnePlus is. In other parts of the world, OnePlus has more dominance (like the Chinese and Indian markets)

One thing to add, the precursor to the 15, the OP 13 (14 skipped due to the number 4 being bad luck in China), was actually the first one to ship with SiC batteries in the U.S.!