You look at this card, and its clearly amazing- but unlike similar"choose" effects, I am always blown away by the fact that you get to pick TWO! Your essentially picking a selection of your choice of solar tide (which also costs six), Purify (cmc 5), or some combination of the two IN ONE CARD (which if you play EDH, I shouldn't have to explain the importance of)

Having those kinds of options, the kind that let you sculpt the board-state to your liking is kind of card advantage that wins you games. Very well designed, very powerful, and yet still fair.