I've worked a lot with C++, and a small to moderate amount with Rust. I tend to prefer Rust when given the choice.
Comparing the overall complexity levels is something of a category error, though. Most of the complexity of Rust is in the core functionality, idioms, and conventions of the language. You'll need to grapple with most of that complexity very early.
Most of the complexity of C++ is in the various functionality that was either inherited from C or accumulated over the decades after that. Most individual pieces of software don't use all of that. E.g. approximately nothing will use both va_list and variadic templates (ok, maybe indirectly through libraries, but not in a way the direct author needs to think about). The latter is just a better way of accomplishing what the former does. There are lots of variations on this theme.
My sense is that, in practice, Rust has a steeper learning curve than C++. I find it more productive now that I'm pretty familiar with it, so I think it's worth that steeper learning curve. I still think it's a bit steeper.
Comparing the overall complexity levels is something of a category error, though. Most of the complexity of Rust is in the core functionality, idioms, and conventions of the language. You'll need to grapple with most of that complexity very early.
Most of the complexity of C++ is in the various functionality that was either inherited from C or accumulated over the decades after that. Most individual pieces of software don't use all of that. E.g. approximately nothing will use both va_list and variadic templates (ok, maybe indirectly through libraries, but not in a way the direct author needs to think about). The latter is just a better way of accomplishing what the former does. There are lots of variations on this theme.
My sense is that, in practice, Rust has a steeper learning curve than C++. I find it more productive now that I'm pretty familiar with it, so I think it's worth that steeper learning curve. I still think it's a bit steeper.