Well, of course browsers are going to render ultimately with the platform's native drawing functions -- which have undoubtably been optimized. The issue is the

Well, of course browsers are going to render ultimately with the platform's native drawing functions -- which have undoubtably been optimized. The issue is the high-level of abstraction between the description of what is to be drawn, and the drawing calls themselves. This is fine for a majority of tasks, but when it becomes a bottleneck your hands are pretty tied. Native apps have much more direct control over threading, vector processing, audio devices, networking, etc.