Which is best for a plant soil with a lot of nutrients or fertilizer?

Soil with a lot of nutrients - generally and theoretically -- is better for a plant than soil with fertilizer.

Specifically, the best possible world is the availability and accessibility of the nutrients which populate soil naturally through the processes of decomposition and erosion. But not all of the necessary nutrients may be there, and those that are in the soil may not be in soluble form or in sufficient quantity. The optimal situation will be the presence in the soil of all of the necessary nutrients and in the macro and micro amounts in which they need to be present and soluble.

Fertilizer constitutes a corrective or supplemental measure. It may be necessary because of what needs to grow or not to grow in the soil. But it also might be a counterproductive or superfluous measure if it is not accompanied by regular soil analyses.