> I know for sure that in the end the C macros will only do text replacement, whereas the Rust macros could do anything.

My impression is exactly the opposite: Rust macros are guaranteed to expand to syntactically valid code that still obeys the memory/type/lifetime-safety constraints, whereas C macros can expand to something that won't even compile, never mind have any guarantees about soundness. Not to mention all the hoops you have to jump through with extra parens and whatnot to avoid the footguns of C macro operator precedence.