It's easier to have more windows on the screen, but it's still no easier to manage them. It's not a problem of pixels, but of cognitive load. For many people simply having more windows visible is distracting, even if those windows are in the background and can be ignored. Its the same reason that people would prefer a clean desk, with only one or a few things on it than one that has lots of things on it. A cluttered desk, no matter how well it's organized, is still harder to manage than a clean desk. A cluttered monitor is the same.
There is probably more work to do out the box to change this perception though. OSX needs to introduce the user to this when they first open an app then make it dead simple to control.
All the more reason not to have a maximize button. Displays only get more pixels year to year.