All four of the current smartphone operating systems support the core promise of the device: quick access to calendar, contacts, e-mail and the Web, as well as the ability to handle third-party apps. That said, each appeals to a slightly different user.The Corporate Exec Windows Mobile for PocketPCs This workhorse of an OS invariably arrives on a large PDA-centric device that´s perfect for editing documents and browsing the Web. With Virtual Private Network software, it´s the most likely to let you fetch your work e-mail.