If you are reloading the OS with the same name, it does not matter if you remove the object from AD. If you will use a different name, then clean up the old object.
1. Reload the system with the same name.
2. Join to AD and take over the existing object. This takes some additional scripting if automating to handle the case of existing object vs no existing object.
If you are simply removing and rejoining a computer, there is no requirement to delete the object unless you think there is a problem with the AD object.