Because carbon-14 decays relatively rapidly compared to other isotopes, it can only be used to date things that are less than 60,000 years old. Anything older would have so little carbon-14 left that you couldnt accurately measure it.

Is relative or radiometric dating more accurate?

Actually none. radiometric dating can not easily be used to date fossils and when the dates between the radioactive dates contradict the relative dates based on fossils the fossils always win.