Box<T> is roughly equivalent to unique_ptr, and you're correct, returning by value would be better. Rust idiom is to use stack allocation and borrowing wherever possible.

> I think the only big difference is that some errors in Rust are happening at compile time.

This is true in these examples, except maybe the enforcement of not using a pointer after you've sent it to a task.

That said, there are other examples, like iterator invalidation, where Rust is completely memory safe, unlike C++. Furthermore, Rust has significantly less undefined behavior and odd edge cases. These are in C++ for good reason, but they're still there.

> with some extra static checking and good guidelines can go a long way.

They can go a long way, and that may be enough for you. Big applications continue to have security issues due to problems that Rust would prevent, though: in the last Pwn2Own, all of Firefox's bugs would not have been possible in Rust, for example.