Hare Krsna,
My understand is that even though both Arjuna and Maitreya saw the universal forms of the Lord, what they saw is slightly different. Maitreya saw the development of the gigantic universal form whereas Arjuna saw the full display of already-developed universal form.
In SB 3.6, Maitreya saw how Lord Karanadoksayi Visny saw the creative functions suspended due to the non-combination of His potencies (twenty-three elements). The Lord sent His cohesive energy which amalgamates all the different elements. Then he entered into the universal fetus as Garbhodakasayi Visnu where all the living entities including the demigods became enlivened as if awakening from sleep. Thus set into action by the will of the Lord, the 23 elements produced the gigantic universal form which is the resting place for all the planetary systems and all movable and immovable creations. Maitreya saw that the gigantic universal form is represented by three (subtle senses, controlling demigods of the senses, gross organs along with sense objects), ten kinds of life energy, and one heart where life energy is generated. Lord Karanodakasayi Visnu, remembering the prayers of the demigods, manifested the virat-rupa by His own energy. Maitreya saw the different kinds of life airs and their functions. He also saw the manifestation of different demigods from the universal form. He saw the development of planets, living entities and varnas. As all the varnas along with their occupational duties are born from the Lord, everyone has to worship the Lord under the direction of guru.
What Arjuna saw is the ‘assembled product’ or full functioning of the universal form. He sees assembled in the body of the universal form all the demigods and various living entities. All the demigods are surrendering and entering into Him. They are very much afraid, and with folded hands they are singing the Vedic hymns. All the various manifestations of Lord Śiva, the Ādityas, the Vasus, the Sādhyas, the Viśvedevas, the two Aśvīs, the Maruts, the forefathers, the Gandharvas, the Yakṣas, the Asuras and the perfected demigods are beholding Him in wonder. Arjuna sees the Lord in His fiercest form. All the sons of Dhṛtarāṣṭra, along with their allied kings, and Bhīṣma, Droṇa, Karṇa, and all our soldiers are rushing into the Lord’s mouths, their heads smashed by His fearful teeth. He see that some are being crushed between His teeth as well. He sees all people rushing with full speed into His mouths as moths dash into a blazing fire. The Supreme Lord is devouring all people in His flaming mouths and covering the universe with His immeasurable rays.
Another similarity is that both Arjuna and Maitreya felt unworthy to describe the Lord’s unlimited glories. Maitreya says that in spite of his inability, he glorifies Lord Hari with whatever he have been able to hear from his guru and assimilate with his intelligence. Otherwise his power of speaking would remain unchaste. Glorifying the Pious Actor is the highest perfectional gain of human speech. The Lord’s activities are nicely put in writing by the learned and the purpose of ear is served by being near them. Even Lord Brahma, after thousand years of matured meditation, could only know that the glories of the Supreme Soul are inconceivable. The Lord’s wonderful potency bewilders even the great jugglers. Even the self-sufficient Lord Himself cannot know it, then what to speak of others? (SB 3.6.35-40)
Similary Arjuna surrenders to the Lord. He says, “O Lord of lords, so fierce of form, please tell me who You are. I offer my obeisances unto You; please be gracious to me. I do not know what Your mission is, and I desire to hear of it.” (BG 11.31)
The conclusion is that words, minds, ego and their respective demigods could not know the Lord. Therefore, we simply have to offer respectful obeisances unto Him.
“The whole world is moving according to the plan of the Supreme Personality of Godhead…What is this plan? This cosmic manifestation is a chance for the conditioned souls to go back to Godhead, back to home. As long as they have the domineering mentality which makes them try to lord it over material nature, they are conditioned. But anyone who can understand the plan of the Supreme Lord and cultivate Kṛṣṇa consciousness is most intelligent…If one is in full Kṛṣṇa consciousness and his life is devoted to the Lord’s transcendental service, he is perfect.” (BG 11.33 P)
“Every plan is made by the Supreme Personality of Godhead, but He is so kind and merciful to His devotees that He wants to give the credit to His devotees who carry out His plan according to His desire. Life should therefore move in such a way that everyone acts in Kṛṣṇa consciousness and understands the Supreme Personality of Godhead through the medium of a spiritual master. The plans of the Supreme Personality of Godhead are understood by His mercy, and the plans of the devotees are as good as His plans. One should follow such plans and be victorious in the struggle for existence.” (BG 11.34 P)
We therefore need to fully understand the Lord’s mission/plan, and sincerely and patiently carry out His plan. Therein lies our real everlasting happiness and success.
All glories to Srila Prabhupada!
Krsna Katha 