The downside of picking subtler, more intricate examples is that you waste your reader's time trying to understand the subtleties of the example, which isn't teaching them anything about Rust.

Another option is to say something like, "For the sake of brevity, this is a very simple and arguably obvious violation of safety. In practice, there are many subtle and hard-to-diagnose sources of unsafety in C++, even when you use safer abstractions like shared_ptr." This allows you to avoid getting sidetracked and losing your reader, while heading off skepticism of readers with more knowledge about C++.