What’s in your pocket? Increasingly, it’s a matter of who pays your monthly cellular bill. Chances are, if you work in corporate America, it’s a BlackBerry device made by Canada’s Research in Motion (RIMM), the company that literally brought the Internet into hands of corporate managers and, importantly, Wall Street.

But if you pay your own way and, crucially, buy your own hardware, even money says you carry one of the various iterations of the hugely popular Apple (AAPL) iPhone.

More than any other single device, the ubiquitous glossy mini-computer has turned the world into a herd of screen-gazing, data-grazing infonauts. Nielsen data show Apple’s operating system now has 27 percent of the post-paid market, as does BlackBerry. (Google’s Android system edges them both at 29 percent but across a variety of other company’s handsets.)

There’s a lot of growth ahead. Consultant IDC sees the smartphone market growing 49.2 percent in 2011 (consumers and enterprise). Vendors will move more than 450 million smartphones in 2011 and the mini computer phones will grow four times faster than the total mobile phone market.

Who wins? Ask the IT department. Mass adoption at the corporate level is a tough nut to crack. But nobody gets past the paranoid tech manager at a Fortune 500 firm without first addressing these three key issues:

Is it secure?

The Apple world built by CEO Steve Jobs has been a great success as a consumer ecosystem. From iTunes to the Mac desktop to the iPhone, users need not even touch a Microsoft product to interact with their digital life. But even the closed system has intruders, namely, malware in the applications. It’s sort of a sign of sickness that BlackBerry has tried and so far failed to come anywhere near Apple in this realm but, like Apple before it, less users has meant fewer high profile scams and attacks.

Only a few months ago, German researchers demonstrated in a web video now to beat a “locked” Apple iPhone in about six minutes. It’s a complicated process, but hackers who are determined could pull it off, they said.

"As soon as attackers are in the possession of an iPhone or iPad and have removed the device's SIM card, they can get a hold of e-mail passwords and access codes to corporate VPNs and WLANs as well," said the researchers from the Fraunhofer Institute Secure Information Technology in a statement. "Control of an e-mail account allows the attacker to acquire even more additional passwords: For many web services such as social networks the attacker only has to request a password reset."

Is it scalable?

IT needs to be able to plug a mobile system into the backend they have, not the backend they can imagine. And, frankly, most of the corporate world lags. It’s a huge investment to refresh servers and systems even every 10 years, which is less time than the iPhone has been on the market in a big way. Sure, a 13-year-old can get an Apple account up and running in a few minutes, but he or she doesn’t have to make that work across 15 offices and hundreds of demanding executives while maintaining connectivity to key office data and software. Until the standards are completely vanilla across all systems, don’t expect mass IT adoption, and don’t expect it even then.

Is it “enterprise” enough?

We’ve been here before with software and hardware. Nothing matters if the end user doesn’t find the product vital to business. Smartphones might replace laptops for a lot of business uses, but probably not completely. But can Apple unseat the BlackBerry’s hold on the executive imagination? RIMM has been moving toward making its phones more iPhone-like (with mixed success), but it seems highly unlikely that Apple will invade the enterprise space anytime soon. Consider its track record vs. the PC.

As they say in business school, don’t get caught in the middle of the market: Either sell mass or sell up. Apple has never been interested in mass pricing or mass markets, and only stoops to that audience with “mini” versions of its products that offer less, not more.

Verdict: Mixed. BlackBerry is safe for now, if only because IT department lag has created a moat for them. But being in the moat is slow paddling for any investor seeking growth. If RIMM can come up with the next generation of business tool, please the IT management, and rebuild its brand, expect at least continued success. Is that the same as growth? Unfortunately, no.

The punchline? IDC sees Android at 45 percent of the market by 2015, with the Windows smartphones second at just under 21 percent thanks to its deal to provide software for Nokia in place of the Symbian operating system. It doesn’t hurt that IT managers already know how Windows works inside and out.

"Up until the launch of Windows Phone 7 last year, Microsoft has steadily lost market share while other operating systems have brought forth new and appealing experiences," IDC Senior Research Analyst Ramon Llamas said. "The new alliance brings together Nokia's hardware capabilities and Windows Phone's differentiated platform. We expect the first devices to launch in 2012."