“So there is no real halachic plusses to wearing a long jacket?”
Hardly. There is an element of Tznius, so that’s enough to make it matter in a Shaas Hashmad, being a Tzad Yehadus. I saw someplace that the Chazon Ish held it is Tznius thing.
There is a hint to this in the Gemara in Shabbos, in which Rav Yehuda illustrates how the overcoat, the Glima, is related to Golam, that you don’t see the limbs but only one solid form. The assumption is that he said this as a positive attribute.