Yogic Meditation VS Hari Kirtan
In all Vedic literatures it is confirmed that one must meditate on the Supreme Absolute Truth, Visnu, not on anything else. But there are different processes of meditation recommended for different ages. The process of mystic yogic meditation was possible in Satya-yuga, when men lived for many thousands of years. Now people will not believe this, but in a previous age there were people who lived for one hundred thousand years. That age was called Satya-yuga, and the meditation of mystic yoga was possible at that time. In that age the great yogi Valmiki Muni meditated for sixty thousand years. So that is a long-term process, which is not possible to execute in this age. If one wishes to conduct a farce that is another matter. But if one actually wants to practice such meditation, it takes an extremely long time to perfect. In the next age, Treta-yuga, the process of realization was to perform the various ritualistic sacrifices recommended in the Vedas. In the next age, Dvapara-yuga, the process was temple worship. In this present age the same result can be achieved by the process of hari-kirtana, glorification of Hari, Krsna, the Supreme Personality of Godhead.
In this age, Kali-yuga, one cannot execute any process of self-realization or perfection of life other than kirtana. Kirtana is essential in this age.
From – The Science of Self Realization
By His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada