What's the difference between Rare, Epic and Legendary dragons in Dragonfire?

Game of Thrones: Dragonfire has 3 rarities: Rare (🔵 blue), Epic (🟣 purple) and Legendary (🟡 gold). Rarity decides two concrete things:

• How strong the habits are at their base. A level 1 habit is worth 250 Power 🔥 on a Rare, 340 on an Epic, 420 on a Legendary. At level 5: 1,800 / 2,500 / 3,100.
• How hard the dragon is to raise: upgrading a habit needs a Core of the matching colour (blue / purple / gold). The gold (Legendary) Core is the hardest to farm.

So Legendaries (Syrax, Crimson, Seasmoke, Caraxes…) are the strongest but the slowest to finish. Concentrate your gold Cores on them, not on the whole roster.