i don't think there is any reason for b minus tree to exist

redhumor

[size=4]first,when data is too large,we can built muti-level index using b plus tree.
when data is not so large,we can use AVL tree.
when we use b minus tree, if the tree node is constitute by array ,then it's slow when insert one element than AVL tree,
and if the node is listing,then it's slow when looking up the element than AVL tree.
So my question is : is any use of b minus tree?
thanks a lot[/size]