I've been riding to the William all season and just recently switched to the Bill (same shape) for the park.
I've ridden the Code and the William and I rode both very well. I leaned toward the William for a couple of reasons. First, It is fast. It is faster than the Code. Don't let 3 stage versus continuous fool you. The Continuos on the Code is an accelerated type where the William, though it has 3 stages blends the rocker from belly to tip. Second, the william has a groove that runs the length of the board just inside of the rail. I think they call it "grip and release," but the difference I have found is that it really allows you to develop a steep angle toward the wake with out tipping the board so far on edge (and throwing off your body position). The last reason I chose the William is because it allowed for a variable approach. I am a mood drive rider. Some days I air it out and some days I go wake to wake on everything. Some tricks I edge smooth and steady and sometimes I like to chop at the wake. I really felt like the William was a more versatile board for me.
All that said, most people in my crew have been leaning toward the Code. It is an absolute workhorse. Smooth turning, long approaches, extremely consistent and pops really well. Pretty much everything anyone wants in a board. The one thing the code does to better than the William is drive through the wake. That is one of the toughest things for a developing rider to get over and the code facilitates that very well.
That was a lot of words with out much help on your pick, but honestly, both are a great choice. You can't go wrong with either of these boards.