The caller ID is only part of the screening process. It doesn't matter if the caller ID is faked or not.
Known/approved callers logged in the phone/device address book ring straight through. Anyone else is challenged to state who they are and press a key on the phone. Only then does the customer's phone ring and they hear the announcement from the caller and can accept/reject the call. Any caller not completing the screening process has their call dropped without the customer's phone ringing.
Greatest benefit is against the automated diallers which cannot comply with the button press and so those calls are dropped without the phone ringing. Either of the devices mentioned restores the phone to normal use without having to manually screen calls and decide whether to answer or not. Even if a scam caller breaks through the first layer of screening, the recipient can still reject the call without speaking to the scam caller.
Just a matter of how many scam calls you receive each day and how much they annoy you as to whether the devices are VFM or not.
