privacy.resistFingerprinting is too blunt an instrument, one that fails to offer selective countermeasures. For example, it prevents Firefox from opening to a user's predetermined window size. The "strict" setting provides a bushel of fingerprint protections — some clearly useful, some counterproductive, others unknown and invisible. Users should be free to pick and choose those actions appropriate to their systems and installations.
I use a few fingerprint defender extensions, but none address the full range of options offered by the privacy.resistFingerprinting setting. Being forced to accept all or none can leave users vulnerable to fingerprint tracking while defeating user customization.
Fingerprint defender extensions don't help. It's like hiding a pothole with a board. The pothole is still there, but there's a fairly obvious board covering it now.