I've had both in my towns at one time or another. Given they have different personalities it makes it difficult to choose. If I were forced to make a decision however, I would go with Skye.
Omg this is so hard, I love both and have had both (Whitney moved out sadly without telling me). I actually think Skye is the villager I've had in my town for the longest time without moving, and that makes her even more special. She really cares about my mayor and that's so sweet. So I will go with Skye <3