For productivity, ignoring the aesthetics of letterboxing for videos or games, aspect ratio comparisons really just come down to more resolution/desktop space is better. A 1920x1920 monitor is "squarer" than a 1920x1080 monitor, sure, but you can also just think of it as a 1920x1080 monitor with more space in the vertical axis. For productivity, making either axis longer or higher resolution is just better (obviously until you approach extremes which are physically unwieldy).