The COFFIN system is called so (c'mon, there is not way this acronym wasn't intentional!) because the pilot lies on his/her back, closed in from all sides. In modern planes, the pilot is usually seated to give them a better view and more intuitive controls but they are also more prone to blacking out from excessive G-force, because human body can take much less Gs longitudinally than laterally. Now, in an advanced airspace display like COFFIN, there is no need to have the pilot seated to give him/her 360 degree view, while laying them on their back would allow them to pull much sharper brakes and turns! The matter of ejecting from a COFFIN is still open, however... unless Fridge Horror applies here, as well. — Koveras
Fridge Horror definitely applies here. All of the benefits to the COFFIN system above? They come at the cost of having no ejection system - if you get shot down, that's that.