My “ideal” mobile device is designed from scratch for its form-factor, allows me to communicate wherever in the world I am, holds all my important data, allows me to search it, identify relationships between it, and interact with it in a consistent and human-friendly way, doesn’t “own” my data or lock it into a particular platform.
Beyond that, any CPU that is sufficiently responsive is fine.
Steven describes his ideal mobile device and why the hardware should be the least of the concerns. Many good points here.