I normally use "more space", as it's the only option that can give me the screen real estate I had with a 17" MBP.
Not really a dealbreaker (the current Retinas are great and I can live with the slight decrease in sharpness), but if in the future Apple finally gave us a 4K MBP with a 3840x2400 native resolution and integer scaling to 1920x1200, I'd be more than happy.