There can be more to "speed" that just execution time of your code. If you need to add an index to help performance, then a Caché SQL query will be able to utilise it without any code changes. If you are using $Order, then you need to spend some time writing and testing your new code.
I typically use SQL to identify objects, then Object methods to interact with them, but for simple updates of large numbers of objects, I'll usually use a simple SQL Update. The beauty of Caché is the flexibility to use the best tool for the task at hand