Soil is a deep subject. Pun intended. Not all soils are created equal. Some soils are more nutrient dense than others. It's important to understand, over time soil will be depleted of its nutrients by the plants rooting in it.
The most nutrient rich soils can supply a cannabis plant all the resources it needs over its life time. This doesn't mean the plant will bear the best results possible. No matter which soil you choose, a feeding schedule is highly recommended.
Coco coir is the by-product of processing coconut husk fibre. It does not contain any nutrients. Coco requires you to provide all the necessary nutrients when watering.
It has several advantages:
Its biodegradable, holds moisture and the nutrients in it, provides aeration in the soil that roots love and retains a constant pH of 5.2 to 6.8.
Coco requires you to be more attentive with your feeding schedule since it does not contain most nutrients that your plants need. In addition, lower grade coco can be high in salt, requiring you to wash it thoroughly before planting it it.