Every recursive function can be rewritten as a loop, and every loop can be rewritten recursively. Why does the choice between them still matter?

C. Because one of them usually matches the shape of the problem.

The equivalence is real and the ergonomics differ: a tree is a node with subtrees, so a recursive traversal mirrors it, where the iterative version maintains an explicit stack. Recursion costs a frame per call and tail-call optimisation removes that where it is guaranteed, so decide on clarity, and check depth when input could be large: a million-element descent exhausts Python’s stack.