How much better is this dynamic approach than something like immutable strings? (not that char* is immutable) Since with the sds library, you could potentially

How much better is this dynamic approach than something like immutable strings? (not that char* is immutable) Since with the sds library, you could potentially be getting back a new pointer for each operation, you could just as easily be working from an immutable string library. Do immutable strings have poor performance? I've never really considered it.