I used to be for making it a side tier,but after like a hundred battles with WiFi on it grew on me.
I'm currently voting for WiFi,as it makes the game less of a coin-flip and more of prediction.
However as has been previously stated,there is still a large luck factor involved,as there is no guarantee what set your opponent is running.
Also on a side note WiFi makes pokemon Like Zoroark and Ditto less useful than without,as you can predict what pokemon they are liable to want to transform or disguise as in the case of Zoroark.
I would like to clarify that this post is from my point of view and i would like it if you do not get rude at me or throw unnecessary insults my way.