Levistus's_Leviathan
5e Freelancer
Dragonborn almost never have tails in official art and never have wings. Draconians have tails and almost always have wings. That's the main visual difference. Also, there are more "color variants" of Dragonborn than of Draconians.What's the difference? I don't mean to sound flippant, it's a serious question because I can't tell the difference between dragonborn illustrations and the top image in the OP.
Maybe that's why I've never been a huge fan of dragonborn, because I grew up in D&D with draconians being the bad guys.