User blog comment:BlitzerRyuusei/Rating supports by their poke, sustain, and burst/@comment-6301771-20131010193309/@comment-35019468-20131011223452

Leona's base health regen is one of the highest in the game; but she doesn't heal or peel easily for the ADC. Her sustain is not that great.

is expensive, low-damage, and best saved for CCing, while Sona's and  do high amounts of damage, even if they're short-ranged. Sona's poke is pretty damn good.