"Lord Śrī Kṛṣṇa is thousands upon thousands of times more satisfied when He sees Śrīmatī Rādhārāṇī's face light up from this combination of ecstatic love than He is by direct union with Her.
This is further explained in the following verse from the Ujjvala-nīlamaṇi (Anubhāva-prakaraṇa 46) of Śrīla Rūpa Gosvāmī.