Q 92 What races gains the most benefit by going dragonborn, other than kobold (which pretty much only loses the +1 natural armor)?
A 92: Elf ranks right up there, but ultimately probably the Buoman (+Wis outsider race that loses it's no-speaking restriction).
Elves have about four things that they'd lose.
Where are Buoman from?
All Elves really lose is their con penalty and dex bonus. IIRC buoman are from the Planar Handbook. The race is moderately detailed in the Cleric handbook here, and possibly the druid one as well.
Actually, it's six things. They also lose their +2 Listen, Spot, and Search bonus, their ability to detect secret doors, their weapon proficiencies, low-light vision, immunity to sleep effects, and +2 bonus against enchantments.