Word on the street is that second children tend to be more reserved and later to speak than their older siblings. This is often the result of the big brother or sister speaking on behalf of the little one or just plain talking louder. Couple this with the fact that, once you have two children, you are more distracted, so as a parent you read less to, and likely focus less attention on, your new addition than you did on your firstborn.
So far this hypothesis does not appear to be holding true for AK. She has been talking up a storm lately and has way more words that we give her credit for. Five new words pop up every day - from "umbrella" and "bird" yesterday to "Melmo" - her favorite Sesame Street character. In addition, she is a voracious reader. I have to "read" at least four books a night to her. Fortunately, this mostly involves looking at the pictures and asking her to show me something in particular. And man, if she isn't spot on every time!
Watching AK do things - like removing her shoes and socks and tucking her socks into her sneakers - really brings back memories of LP starting to do the same things. Then again, they are really very different. Even looking back on my post from almost exactly two years ago when LP was going on antibiotics for the FIRST time. AK definitely has her beat on that front!
In terms of personality, LP has always been quite social and she definitely has a "mothering" instinct. She always tries to take care of her friends and we frequently get notes on her daily sheet that say she was a good helper to her friends and teachers. AK is more focused on herself. And being an entertainer. She is incredibly silly and she loves attention. And she has no fear - not of hurting herself, or animals, or food. This is quite different from LP, but I can't recall if that set in later.
In fact, instead of being outshone by her big sister, I think AK is challenged by her. In reality, AK thinks she is three and a half. She walks into LP's classroom like she owns the joint and seeks out activities or toys. AK wants to do everything like LP, from putting on LP's coat and hat to eating her food (literally, taking food off LP's plate when she has the identical items on her plate) and drinking from her cup.
Note, I am a second child and can't remember a time when my older brother was louder than me. He often overshadowed me in the classroom, but I think I have the edge on the volume and social fronts. I am sure he will correct me in the comments if I am wrong.