Actually, he took both routes. The thing about both is that they are outside influences on the individual and on personality. It was the general assumption in his day (1890s - 1910s) that personality was caused by such outside forces. So it came as a surprise and delight when, in 1910, he told all his followers that they MUST agree with him, that sex (an internal force) is the only determinant of both normal and neurotic personality.
A dozen or so did not agree, led by Freud's co-worker and equal (NEVER his student, follower, or disciple!) Dr. Alfred Adler. In February of 1911 Adler debated Freud on the influences on personality disorders and development. Among other things, he spoke of the "masculine protest" that women, and some men, had to make against their definition as females/males by the dominant male social structure.
Also, Adler confronted the thinking that insisted on outside forces as determining personality and psychological character. He said that while nature, nurture, environment, heredity were important, just as important was the individual's creativity, and the choice that is available by making use of one's free will. Adler called this approach "soft determinism" and of course it became the dominant idea in psychology and in the whole field of human development from then on. Today no one would argue that only outside forces (only nature or nurture) have any effect on personality development.
So it sort of doesn't matter what Freud assumed. It was Adler's concepts that carried the day and Freud's ideas that got left in what's been called "the dustbin of history."
-- Dr. Bob, Adlerian Psychologist