You need to understand that Global Illumination is a "generic term" for advanceddlighting techniques. Inside this term of GI, there are quite a few different solutions, from quick to very slow.
What Vue calls GI is the accurate computation and spreading of shadows, which means that it does not compute bouncing light. It justs spreads the shadows of every light source in the scene in an accurate way. So your scene will be a lot darker, Vues adds realistic shadows, but no additional lighting, and the more lights in the scene, the more shadows. GI is best used for outdoor scenes, where the light and shadows come only from the sun., otherwise, it gets too dark, like here.
Radiosity is the most advanced lighting model of the GI models. And the slowest too.