Hi @Mahesh_Gunaje ,
Compared with JS logic, Sling rewriters can offer better performance because the modifications are applied on the server side before the content is sent to the client. Considering good practice it's always better for future management. However, it's important to keep in mind that any server-side processing can introduce overhead, especially if the rewriting logic is complex or involves iterating over a large number of links.
If the rewriting logic doesn't depend on dynamic data or user-specific information, consider caching the rewritten content to improve performance further. Ensure your rewriting logic is efficient, optimized and avoid unnecessary iterations or computations.
If you still want to see the visual effect rather than the theoretical talk, you can perform a load test. One is without a transformer and another one is after adding the transformer code.