The most important thing is to get a kayak that fits you well. Most beginning whitewater kayakers will feel most comfortable in a general river running design of which the Dagger Mamba is an excellent example. Some other popular models are the Wave Sport Diesel, the Jackson Karma and Zen, and maybe the Pyranha Burn.
As for the Wave Sport Big EZ, I have one, and it is not a bad boat. It was designed by Eric Jackson to be more of a play boat. It is slower than many river runners. It has a scalloped out “duck bill” front end that was designed to cut vertically through the water for cartwheels and allowed the front deck to be easily loaded for loops and such. Those are features that you definitely don’t need, but I have had a few beginning whitewater kayakers in it and they did reasonably well, so I would not rule it out.