Some quick differences. From the old DD we lose +4 Str, +2 Cha, Bite, Full attack of claw, claw bite, immunity to energy type, immunity sleep and paralysis, darkvision 60', low-light vision, type change to dragon.
You can get your immunities if you have 10 sorcerer levels in addition to DD, otherwise not... so I expect for most its a loss.
The new DD has over the old, 4 bonus bloodline feats, 1 more AC bonus, more powerful and magical claws, 7 additional caster levels (with some bonus spells known (probably 3), a stronger breath weapon usable twice per day instead of once, and Form of the Dragon II 2/day.
I would instead add a bite at 2nd, introduce Power of Wyrm at 10th, along with +4 Str, +2 Cha, Dark vision, light vision and type change to dragon. Now you are essentially a half dragon + some. In exchange I would drop 2 spell level increases, two bloodline feats, and the form of the dragon.
You end up with a little less potent spell caster, but you have put the Dragon back into the Dragon Disciple.