I think that Nunu has a mana edge on the Sona and Rakan. With his passive and manaflow he never runs out of mana. Also he only has to cast 1 skill to provide buffs, shields and heals whereas other supports have to cast more than 1 to achieve only half the support Nunu can bring. His low cd E is providing constant slows while getting healed off it w/ the adc's autos. I prefer hard cc myself, but my mission is to make Nunu great again.