speed of preorder traversal

It's not answerable in the abstract, without a lot more specifics. It depends on intimate specifics of the computer architecture, what counts as "one" operation, how the tree is represented, and many other details that are usually considered a distraction for purposes of analysis of algorithms. And it wouldn't really be useful in practice anyway; these days, the time it takes for an algorithm to complete depends on a lot more than the number of operations. Not all operations take the same amount of time, and more importantly, the memory hierarchy plays a huge role in influencing the running time, and you can't measure its impact by counting operations.