My wife and I have sailed on just about every class of ship Carnival has and the Vista class is way more crowded. We have been on both the Vista and the Horizon and have determined that we will not be going back. They added a lot more cabins and made the public areas smaller. How could it not be crowded? The vista class were clearly designed by accountants to maximize passenger count.
Now before you jump on me and say I am just a hater, I am about to Diamond and love Carnival. I have two more cruises booked for January. As an engineer I just don't think the Vista class was designed well.