In case somebody stumbles upon this conversation in the future: I just migrated a project to use smartstrings and it works a bit differently from smallvec. Smallvec lets you decide how big you want to make the static buffer before it allocates, whereas smartstring's static buffer size is alsways `size_of::<String>() - 1`, that is 23 bytes on 64 bit architectures and 11 on 32 bits. If I want, say, a static 128B string smartstring won't do any better than std::string::String.

It's still a very nice lib though, and a smart optimization, but it doesn't cover all of my use cases for small string buffers.