[Python] Why using 'or' here for tree traversing is faster?

I am solving for the Leetcode problem 104. Maximum Depth of Binary Tree. What I realize is that for the line findDepth(node.left, depth+1) or findDepth(node.right, depth+1), if I change it to findDepth(node.left, depth+1) \n findDepth(node.right, depth+1), though the output is correct, the runtime increases from 1ms to 7ms. I am confused since the findDepth function will always return None, thus both sides of the 'or' will be executed anyway.

class Solution(object):
def maxDepth(self, root):
"""
:type root: Optional[TreeNode]
:rtype: int
"""
self.max = 0

def findDepth(node, depth):
if not node:
return None
if depth > self.max:
self.max = depth
findDepth(node.left, depth+1) or findDepth(node.right, depth+1)

findDepth(root, 1)
return self.max


I will like to know the differences between the two lines(with and without or).

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