”の“ and ”が“ originally meant the same.
"の“ meant, and still means, "genitive" in the old days.
And "が“ also meant "genitive".
(It still remains in the phrase "我が祖国“, my country)
Historically "が“ acquired the new meaning "marker for so-called 'subject'".
That's why 1). there are two expressions:
背の高い男の人は....
背が低い男の人は...
(These の and が, I think, are marker for genitive, not for subject)
and 2). you can say "あの人は背が高い“ but cannot say "あの人は背の高い“.
(”の“ cannot be marker for subject)