The philosophy of yoga is to withdraw the mind from external activities, to draw its focus inwards, and to bring it into deep concentration. The resolution of mind acquired from sleep is of a Tamasic nature. But the quality of mind (concentration, strength) acquired from yoga Sadhana is of a pure Sattva guna.
That is the difference between the two. It goes without saying that the mental strength acquired through a base of Sattva guna is superior to that acquired through a base of Tamasic nature. Whatever health, strength and happiness is acquired through normal sleep is exceeded more than 1000 times over by the strength, health and happiness acquired from the mental strength one develops through the practice of yoga.
Ordinary people will not understand this. The mental concentration and strength acquired through yogabhyasa is called yoga nidra and ordinary mental resting which is Tamasic in nature and is acquired as a result of physical exhaustion is called ordinary nidra.