Do you think gamefreak would ever add a feature to let the player replace the ball their pokemon is in with one in their bag?
The only effect it has is cosmetic, though I could see an argument for balls being a legality check in competitive, though it only applies to a small percent of combinations.
On an unrelated note, does anyone have a preferred "default" ball; that is, a ball you tend to like on almost any mon. For me it's luxury or timer.