Symbian is made from the ground to be a mobile OS. Linux is just a hack of an old OS for switchboards. Symbian is better integrated with hardware and runs more efficient. Better processors and HW in general makes this difference smaller, especially or high end devices, and Linux is much simpler and more flexible. Linux is like Windows (desktop), sloppy, imprecise and power hungry (but powerful with enough CPU), and Symbian is more like a real time OS similar to Windows CE.