>Magikarp
Sun: Magikarp is weak but has great fertility. You can see it everywhere.
Moon: Many pokemon feed/survive on Margikarp because it just splashes recklessly.

>Spearow
Sun: Spearow has short wings and is not good at flying. It feeds on Bug Pokemon in grass.
Moon: Spearow has a big appetite. It's essential to farmers who are struggling with pest Bug Pokemon.

>Fearow
Sun: Fearow has good stamina. It can fly with heavy load with ease for a day.
Moon: Fearow-like Pokemon was found on ancient wall paintings.

>Pinsir
Sun: Pinsir can cut its opponent in half with its long horns. Although it's powerful, it struggles in cold weather.
Moon: Pinsir can break a wood in half with just one strike from its horns. Vikavolt is its biggest rival in Alola.

>Golbat
Moon: When Golbat sucks too much blood, it will become too heavy to fly and fall to the ground, thus hunted by other Pokemon.

>Dratini
Sun: Dratini grows bigger as it sheds its skin. Boots made of its shed skin are luxury goods.
Moon: Dratini was discovered by a fisherman who spent 10 hours and eventually hooked it.

>Dragonite
Sun: Dragonite will bring the rescued man to an island where it's the paradise of the Dragonites.
Moon: Dragonite is usually a mild-tempered pokemon. However, once its Reverse Scale is touched, it won't stop until destroying everything.

http://www.pokemon.co.jp/ex/sun_moon/pokemon/