Parents of more than 3, which transition was hardest on the children?

For those who've had 3 or more, did you notice a difference in how hard it was for the children to adapt to the new additions?

For example, did your oldest have a hard time with a new sibling but then additional siblings weren't as hard for them? Did the second adapt easier than the first when baby 3 was born because your second was already used to having a sibling?