Honestly, after trying out both games I would have to conclude that Wizard101 is better in terms of content, graphics (except Avalon), and just general gameplay. But as most people will argue, the game starts of slow and gets a little more interesting. I will definitely find out though. Some people are criticizing the fighting style of Pirate101 but I say that it's more complex and different then Wizard101 (plus, I love how you do those EPIC slow motion moves).
I would have to say that I like wizards in general because you can cast spells and destroy your enemies in a more amusing way.