Using a 2-3-4 tree instead of a splay tree

Question

I'm in a data structures course right now and we learned about 2-3-4 trees and splay trees. I was wondering in what circumstances would you use a 2-3-4 tree instead of a splay tree? They're both self balancing and sorted so I don't see that much of a difference between them.

Answer 1

A 2-3-4 tree only changes the structure on insertions and deletions, while a splay-tree also re-organizes the nodes on searches.

Splay trees will, thanks to the re-organization on lookup, provide faster responses if your typical usage pattern happens to look up a small subset of elements most of the time.

It is possible to implement a 2-3-4 tree such that the smallest element can be looked up in O(1), but generally both offer insertion and deletion at amortized O(log n).