Smartphone-Chan benefits from superhuman multitasking, computation, and [photographic] memory. But its powerful intellect and energy means it burns out quickly, sometimes becoming caught up too deep in thought to the point of losing concentration. Beside this, it also experiences peer pressure and competition with its siblings (Iphone, Samsung, Android, etc).
On the other hand, Cellphone-Chan has the IQ of an average Joe; it does its job simply and reliably. Unlike its rival, Cellphone-Chan has plentiful energy to spare, never having to do so many things at once. In fact, its simplicity is its greatest strength - its plastic exterior is denser and provides greater coverage. If anything, it will crack the floor/wall or shatter the window/windshield without flinching - something its rival can never do reliably. The best news of all: Any damage or abuse costs half as much as Smartphone-Chan (sometimes a quarter of the price).