Windows Mobile – offer a familiar Windows-style appearance for business users, along with simple data syncing with Microsoft Outlook.
BlackBerry – Traditional BlackBerrys, such as the 8700 series, sport spacious QWERTY keypads for quick thumb typing, while the smaller Pearl models use a technology called SureType to allow fast typing with multiple letters assigned to each key.
Palm Palm Treo smart phones maintain a prominent place among business handsets, thanks in large part to their simple interface. Palm has extended its offerings to include Windows Mobile as an option, and also offers BlackBerry Connect service, which makes it a viable choice for larger business networks. Link