Are OTC pain medications safer than prescriptions?

Are pain medications that I can buy Over the Counter (OTC) any safer than prescriptions I receive from a doctor to manage pain? For example, I have migraines. There are several OTC medications advised for migraines: - Acetaminophen/Paracetamol - Aspirin - Ibuprofen - Naproxen While my headache specialist has prescribed several other medications for my pain: - Imitrex (and other triptans) - Midrin - Prochlorperazine - Cambia - Anaprox Are the OTC pain medications safer? Why are some pain medications OTC and others only available by a prescription?