Rising Strike is probably best all-around because of the high damage modifier combined with one of the quickest knockups in the game.
Spinning Strike puts up big numbers that look good in screenshots, but it's outdamaged by Rising Strike in most situations based on speed and number of targets, not to mention the lack of utility.
Gravity Strike probably does good damage once you add up all the hits, but the lack of an early knockup and the annoyingly long animation for the second part put it at a disadvantage.
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