(Kadamba Kanana Swami, 25 July 2013, Durban, South Africa, Srimad Bhagavatam 1.3.6)
In the maha-mantra, there is a relationship. There is Krsna, the all-attractive Supreme Lord, and the vocative form of Hara which is Hare and that is the hladini shakti, the pleasure potency – pure devotional service embodied by Radharani, but also referring to any devotional service.
Hare represents devotional service to Krsna, and Ram represents either Balaram or Lord Ramachandra. Balaram is the embodiment of ecstacy, and is particularly the one who gives spiritual strength. So from serving Krsna, comes Ram, which is spiritual strength and ecstacy. Therefore transcendental happiness is experienced when chanting Hare Krsna in devotional service to Krsna.
Even when referring to Lord Ramachandra, who is the embodiment of religious principles, one becomes pure and the embodiment of religious principles when chanting. So it is interesting that all these things are there within the name. If you just chant other names of the Lord, that relationship is not there. Therefore it cannot compare to the maha-mantra.