In plain words
Rāma is the one who went to battle when His foot was trodden on. Kṛṣṇa is the one who trod on the foot and went to battle. Ready to fight with everyone, Kṛṣṇa went on defeating everyone. That is the very difference between the Tretā Yuga and the Dvāpara Yuga. The Kṛṣṇa principle is a principle full of Ānanda. The Rāma principle is the principle of responsibility. The Rāmāyaṇa came to proclaim Satya, Dharma and valour to this world. ‘Rāma ayanaṃ, Rāmāyaṇaṃ.’ The Kṛṣṇa principle is not like that. It came to teach the world. He desired nothing for Himself. He tied nothing to Himself. He went on giving everything to the people. He killed Kaṃsa. He gave the kingdom to his father, Ugrasena. He did not take it Himself. Siding with the Pāṇḍavas, He defeated the Kauravas and had Dharmarāja crowned. He asked for nothing for Himself. He was a mahārāja without a crown. The King of kings. Of His own He had no kingdom at all. The hearts of all are His kingdoms! Such is the truth that the Kṛṣṇa principle taught.
Each Avatāra Came to Give Its Own Ideal!
When you truly inquire, each Avatāra has come forth to give an ideal of its own! The Gopīs came and kept making complaints to Yaśodā. Whether Kṛṣṇa spoke in fun or in any other way, it was all Satya! Not even in jest did He speak Asatya. Those who could not understand thought that what Kṛṣṇa said was a lie. In every age it is the same sickness. The Gopīs came,
At midnight Kṛṣṇa climbed onto our terraces and came, tied together the braids of the sleeping women and came running away; Mother, ask Him, Mother, ask Him!
So they complained. Then Yaśodā:
At midnight, what business have you in other people's houses, boy? They say you tied the braids of the sleeping women and came running away! Kṛṣṇa! Leave off, boy...