You can flash it straight to 1.4.1
You could also flash it from 1.4.1 to 1.4, it's basically rewriting it completely.
Flashing is also good for unbricking Acekards.
Remember to pick the right file for your system, DSL.nds will only work on a DS Lite since it switches cartridges to do it. DSi.nds doesn't need to switch cartridges, so it can only work on a 1.3 DSi.