Tamas, rajas and sattva have the respective qualities of obscuring, agitating and revealing knowledge. Of these sattva is the best because it is not unfavorable for suddha-sattva. This is shown through an example. Superior to wood — which is devoid of the quality of action and unable to reveal its nature (being unconscious) — is smoke. Smoke has an active nature. Superior to smoke however is fire, which has the qualities of action and revelation. It is called trayimayah (related to the Vedas) because it is used in rituals mentioned in the Vedas. Rajas, which is agitating, is superior to tamas which is inert. Sattva, being devoid of inertia and agitation, is superior since it gives a vision of brahman.

sattvat sanjayate jnanam rajaso lobha eva ca
pramada-mohau tamaso bhavato ’jnanam eva ca

Knowledge arises from sattva. Greed arises from rajas. Inattention, confusion and ignorance arise from tamas. BG 14.17

It is not obstructive to suddha-sattva and does not cover it. It does not interfere with seeing brahman. It is thus an assistant in spiritual life. Without bhakti however, seeing the Lord (or even impersonal brahman) is impossible. This is confirmed later in the Bhagavatam.

It is said of the Lord’s form anando brahmano rupam: the supreme lord has a form of bliss. The gunas of maya - tamas, rajas and sattva - cannot act independently of him. Maya paraity abhimukhe ca vilajjamana: maya flees from the Lord, being ashamed. (SB 2.7.47) Thus it is by the will of the lord, by his touch alone, that ananda becomes qualified by agitation in the form of Brahma. Being qualified by revelation, ananda becomes Visnu and being qualified with obscuration, ananda becomes Siva. Since there is no damage when ananda is combined with revelation (sattva), Visnu is worthy of worship.

Because one can realize fire through wood but not through smoke, tamas should be considered superior to rajas. In deep sleep (tamas) one has realization of oneness with atma. Thus some persons argue that between Brahma and Siva, Siva is better.

These three are equal in that they are all avataras of the Lord. They are unequal in that Visnu is not covered by the gunas, whereas Brahma and Siva are. This is how the contrary statements of difference and non-difference of the Puranas can be harmonized.

The sruti says asango hy ayam purusah: the atma is not contaminated by the gunas. (Brhad Aranyaka Upanisad 4.3.15) Though both Paramatma and jivatma are by their constitution devoid of the gunas, because Paramatma is the supreme lord, an ocean of cit, because he is independent in his actions, he remains atmarama, self enjoying, not subject to birth in the world, without diminution of his knowledge of himself, even though, by his will, he contacts the gunas and thus is in possession the effects of the gunas such as anger. However the jiva, because he is only a particle of cit, having very little ability of knowledge and because he is controlled by the Lord and not independent, and has very little power, he loses his knowledge of his real nature and takes birth in this world by contacting the gunas where the gunas act upon him.