Decision-makers at small and mid-sized businesses don’t have it easy these days, especially when it comes to deciding what kind of smartphone to deploy among its mobile employees.

This is because there are many operating systems to choose from today, such as BlackBerry, Windows Mobile, iPhone, Nokia’s N Series and Palm OS. There are also various handset manufacturers to consider -- among them Motorola, Samsung, HTC, Apple, and BlackBerry's maker, Research in Motion. And of course, then there are the form factors to consider. Do you go for flip, sliders, or candy bar-shaped phones, each with or without QWERTY keyboards and/or touch-screens?

Before making all these decisions, it's best to address which mobile smartphone operating system is best for your business. In the end, that will likely help narrow down your choices for handset maker and form factor, too. And what of Microsoft’s chances in succeeding in this highly competitive and overpopulated space? Read on.

It’s all in the apps

The first thing you need to do is to research the strengths and applications for each of the smartphone operating systems, says Michael Gartenberg, vice president and research director at New York City-based Jupiter Research.

“Perhaps you need the phone to work with Microsoft Exchange, or maybe you need to create or edit e-mail attachments, such as [Microsoft] Office documents,” explains Gartenberg. “Knowing what you’re going to use the smartphone for, and if it works with your company software and services, will help determine which one you’ll invest in.”

Speaking of attachments, Windows Mobile-powered devices have an edge over the competition when it comes to file support and smooth PC synchronization, believes Ken Delaney, vice president of mobile computing at the Gartner research and consulting group in Stamford, Conn.

“While Research in Motion has done a great job, Microsoft has tremendous back-end services, Windows file support and a host of applications, making it a natural choice for businesses to gravitate to Windows Mobile,” says Delaney.

Windows Mobile is also supported by many manufacturers, which gives the consumer more choice in smartphones, adds Delaney: “More vendors mean more hardware options, including ruggedized PDAs for field applications which you won’t find with other OS’s.”

BlackBerry and Nokia are also major players in the business space, agrees Delaney, but the iPhone has “a ways to go.”

“The iPhone isn’t anywhere yet -- it’s the new kid on the block -- and while intriguing, it hasn’t made its full statement yet,” says Delaney.

E-mail receiving, sending

Led by BlackBerry, most of the major smartphone operating systems support the popular “push mail” application, meaning messages arrive on the phone as soon as they’re received in the user’s PC inbox (if not sooner).

But a user must also be concerned about writing e-mails when out of the office, therefore Gartenberg says to consider the type of keyboard, as well. “Some swear by a tactile keyboard like a BlackBerry, while others like a soft keyboard a la the iPhone,” Gartenberg says. “The key is to try out the phone first to see if it’s comfortable for you.”

While all BlackBerrys offer a button-based keyboard, some models offer a QWERTY layout (including the Curve and Bold), while thinner models (like many Pearl handsets) house a SureType keyboard with two letters per button.

Security, too

Nathan Dyer, senior analyst for enterprise mobility at Yankee Group, a Boston, Mass.-based research firm, says Windows Mobile is “gaining ground” on BlackBerry, the No. 1 smartphone maker in the U.S., because of more vendor relationships (RIM, Apple, and Nokia make their own handsets), strong brand recognition and familiarity, and more aggressive security measures than it did in the past.

“Security had always been lagging in Windows Mobile,” says Dyer. “ActiveSync met most of the minimum requirements for  businesses including ‘wiping’ and encryption -- especially for [small and mid-sized businesses] that didn’t want expensive middleware -- but they’ve only recently stepped up to the plate with new and stronger tools,” explains Dyer.

For example, ActiveSyc only met about a dozen security policies, explains Dyer, but now its service System Center Mobile Device Manager (SCMDM) meets more than 125 security policies.