297. Serialize and Deserialize Binary Tree (Difficulty: **Hard**)

449. Serialize and Deserialize BST (Difficulty: **Medium**)

These two questions both are about serialisation of a binary tree. I see most solutions are similar (using preorder+resusion or BFS).

For BST, its difficulty is medium, easier than a general binary tree. But I don't know why it is easier.

Is there a better solution to serialize the BST rather than the same way to binary tree?

Or the "easier" means serializing the BST is faster than the binary tree?