Mega-malls may be big, but when you need a fart noise generator, sometimes it's the smaller shops that do the trick -- at least that's true of the crop of virtual mobile retailers called app stores.

Without doubt, Apple Inc's iTunes App Store rules the roost. But virtual shopping outposts on BlackBerry and Android phones offer interesting benefits of their own.

Diehard iPhone fans were skeptical that BlackBerry App World from mobile e-mail pioneer Research In Motion Ltd would appeal to the broad range of consumer app tastes.

But shoppers will find that all of the stores -- BlackBerry App World, Apple Inc's app store and Google Inc's Android Market -- work well in practice.

Each offers apps -- small software programs you can download to a phone -- for practical use (news services and weather reports) or special interests (virtual pets or weapons sounds). But the smaller stores have some benefits such as easier searching and flexibility moving between apps.

SEARCHING THE STORE

If you're looking for variety, there's' no question who wins: RIM's store has around 1,000 apps; Google counted roughly 2,300 in March. Both are dwarfed by Apple's array of 25,000 -- and it has sold about 1 billion apps in less than a year.

But because of the abundance, there is room to improve the store's search feature.

It would be nice if the search results came back in more of a catalog, said Current Analysis analyst Avi Greengart. For example, sorting through 100 search results might be easier if they were grouped in categories like gaming or reference.

This is less of an issue in the smaller Android and BlackBerry stores. Still, users might have to invest some time deciding which app they want.

There's a slight case of options overload sometimes, said Dan Jones, a user of G1 Android phone and editor of Unstrung.com web, a wireless industry news site. His favorites are translators, guitar chord guides and social network apps.

BlackBerry App World has a sleek layout for featured apps, as users can easily scroll between displays which include the logo, price and a short description of favorite apps.

In comparison, users of G1, based on Google's Android system and made by HTC Corp, have to select the category for its featured apps and then scroll. To seek a specific Android App, you first click on the menu button to find the search option. Then you select search, type in your term and touch the search icon before your results show.

BlackBerry App World makes it easy by keeping a search box on top of the list. Simply type Sudoku in the Puzzles section and the list automatically loads -- although sometimes the feature causes a heavily used BlackBerry to crash.

SWITCHING BETWEEN APPS

One advantage G1 users have over iPhone users is that the G1 can run more than one app at a time. For example, G1 can automatically broadcast your location, search for nearby friends or let you receive an instant message, all while you're in another app.

Apple's users will have to wait for an upcoming software upgrade for iPhone to get alerts of new instant messages when they are in a different application.

On BlackBerry, some apps were easier to pop in and out of than others.

Each store has its own payment methods. Apple's is often cited as the easiest because iPhone users have already set up an iTunes account, and logged in a credit card, when they buy the phone.

BlackBerry App World customers must have an account with eBay's Inc's online payments service PayPal, a potentially off-putting notion for those unwilling to sign up for yet another service and remember yet another password.

Android Market uses Google Checkout, which requires your credit card details for your first transaction. After that, it stores your information for follow-up purchases.

Prices make a more striking difference. Android and iPhone have lots of free apps and many priced below $1. RIM has some freebies, but its sales start at $2.99 per application.

High fees may encourage better quality, but some users are perplexed. In a user review of the $2.99 Associated Press news app for BlackBerry, one customer opined: Why is iPhone version free?

However, the price tag did not deter others, I had the free version and felt AP deserved its 2.99 one fan wrote.

As to the logic of fart simulators on BlackBerry, which has a big following among business users and politicians: The teenage boy is never too far from the grown up executive, Greengart explained. I think it's great they can say the BlackBerry is not just about email.

(Reporting by Sinead Carew, editing by Gerald E. McCormick)

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