Retained Versus Immediate Mode Rendering

Retained-mode rendering can be simpler to use, because the API does more of the work for you, such as initialization, state maintenance, and cleanup. However, it is often less flexible since the API forces its own particular scene model; it can also have higher memory prerequisites because it needs to provide a general-purpose scene model. Immediate-mode rendering, on the other hand, as offered with WebGL, is much more flexible and can implement targeted optimizations.