I would imagine that AP CS Principles would be better to introduce people who aren’t necessarily interested in STEM as well as those who are. It wouldn’t so much be a pre engineering course as a “general education” course.
I know AP CS A is supposed to be “the” serious CS course but it seems more limited to me, neither tough enough for real CS majors and too specific to interest others, so that I’m not sure what its goal is.
In any case, to answer OP, neither is necessary to apply to a CS major and I would imagine CS ECS would matter more.