From question tags I assume you’re talking about sqlite, though it doesn’t really matter. It’s hard for me to think of a real world scenario, where delete+insert would outperform update in relational database. Each of these commands is there for a reason, and is optimized for a specific task.
Do you have some real problem with performance of your database operations? Or is this a general question? In first case, please describe your issue. In the second, please assume update is faster.