The semantics are very different, even if the syntactic results are superficially similar. In Rust you cannot retrieve the value on success without explicitly handling the error - that's forbidden by the type system. Additionally you can't have an unitialized error result, or force the callee to check the argument for null.

I think the example is pretty weak, because the difference isn't that meaningful in an isolated case. Consider something like parsing an HTTP request - it is difficult to even write the toy example without handling the major error cases. The result is a robust program by default.