I would have to say both have their place, but one thing to think about is that when you use Whirlwind you have your attacks set to 10 a round, so a sword and shield user would be doing 10 attacks with one weapon, as opposed to 10 between 2 weapons. So thats more assurance that the effect of your one weapon will happen, as opposed to the effects of the two... Which in my book is a good thing, as more control = more power!
