Personally I have Whirlpool maxed and dropped Whirling. I like it much better, both in and out of Myth, but for PvP I would take Whirling. For stage though, it is 2 extra hits, 5 seconds less CD time, less mp cost and out damages Whirling. Also good for push back, and it's saved my ass a few times when I was stuck in a dash about to get hit by a OHKO.
But, that's me, and I have a wierd playstyle.