The Zing can cut heavier materials than the Cameo. It also can cut 14" in width. So if you do a lot of vinyl project from a roll, that may be important to you. I know a few people who has the Zing and they would vouch for it.
I have the Cameo and it cuts beautifully. The con is that it cannot handle cutting thick materials.
So it depends on the type of projects you currently do and what you would like to do in the future.