Don Durito
Hero
One's a big bad dragon with five heads and the other is a big bad dragon with five heads.Vague and misleading, especially when weighed against the mountain of evidence that says they aren't the same. It is mainly pointing to a similar conceptual origin for the two.
1) They have different names
2) They have different home planes (Seven Heavens vs Dome of Creation, Nine Hells v Abyss)
3) They have different divine portfolios. (Check the back of the 5E PHB)
4) They have different divine levels. (Lesser Deity vs Greater Deity)
5) They have different holy symbols. (Silver Triangle v Dragon Head)
6) They have independent existences (Paladine becomes mortal, Bahamut doesn't).
7) Bahamut and Takhisis are dragon deities. Paladine and Takhisis are not - their "favoured creations" are elves and ogres respectively.
The rest is trivia

You don't even have to buy a new mini.