In real life, whatever I look at is always in focus. It's actually very unrealistic to simulate depth of field without good eye tracking, because the user will end up looking at things that are simulated as out of focus but should actually be in-focus because the user is looking at them.
If you don't have good eye tracking, then rendering the entire scene in focus is most realistic, as whatever I look directly at will appear in focus and everything else is more peripheral and will be blurred a bit by my optical system anyway.
If you don't have good eye tracking, then rendering the entire scene in focus is most realistic, as whatever I look directly at will appear in focus and everything else is more peripheral and will be blurred a bit by my optical system anyway.