@Qàtrè Placing epithet adjectives in French is not obvious. A good answer there. In your sentences one could see no difference in meaning, or, if one is intended, it could be that when one says L'homme grand porte une cravate the adjective is meant to distinguish the man by size among other men, and Le petit homme porte un pull the adjective is used to give a characteristic of this man and he's not compared to any other person.

I would be inclined to write « Le grand homme » except that it gives the impression of "The great man" rather than "The tall man", so maybe it's to avoid that