Nergal Pendragon
First Post
No. A red/blue dragonborn dragon sorcerer would not spend any more sorcerer points than a red/red one. Both have fire resistance and no one would spend points to get it. But when they fight something with a lightning attack the red/blue sorcerer could spend a point to get resistance (advantage) while the red/red sorcerer would get fried.
The mixed sorcerer has more option while the double sorcerer lacks half of a class feature.
The double-sorcerer, in turn, has the capacity to cast more powerful spells more often through spending the extra points from not having resistance either on spell slots or on metamagic. Since he simply doesn't budget for energy resistance, he's not depriving himself of part of his defense by focusing more on offense, whereas a mixed sorcerer has to decide if defense or offense is the better choice and accept being less powerful in the option not taken.