The reason someone would buy a cordless detector is because they want to be able to hide the thing quickly in a shirt or jacket pocket. In Ontario the police actively look for cars with them especially on the highways coming from the boarder.
So a cordless unit would be about the only non stealth one you could use. Except the cordless ones emit so much signal they are at the bottom of the list for evading RDD equiped police checkpoints.
If Escort make a cordless one that was undetectable by RDD equipment then I am sure they would sell a ton to truckers who have to drive here.