Android Market app developers are a busy group, with the average publisher placing more than six apps in the online store compared to four published by the average iOS developer in the Apple App Store.
"Android developers are significantly more productive than Apple's," said Research2guidance.
The research firm noted, though, that more apps are later removed from Android Market than from the App Store, for various reasons.
Apple still attracts more apps to its store.
The higher average for Android developers led to a total number of apps submitted on Android Market of more than 500,000 in September. At the same time, the number of apps submitted to the App Store reached more than 600,000, or 20% more.
The analyst firm noted the fast growth of Android Market, which is roughly a year younger than the App Store.
"Over the past few months, the Android Market has been maintaining an exponential growth, but is still lagging behind the app store market leader, Apple," Research2guidance analyst Egle Makalajunaite wrote in a post on the firm's Web site.
Research2guidance noted that the total published September apps were later winnowed down by 37% for Android, for a total of 319,161 at the end of September.
At Apple, the total published number was reduced by 24%, putting the active number of mobile apps in the App Store at 459,589 at the end of September.
Apps are pulled for many reasons, including when a developer stops supporting it or it is found to be defective or not compatible with the latest OS version.
Apple is known to have a more demanding set of application submission requirements than Android, Mikalajunaite wrote.
"It is likely that the more rigid application submission requirements [at Apple] prevent developers from publishing multiple trial or low quality applications, whereas publishers in the Android Marketplace a lot of market testing, trials, demo and malware content," he noted.
Nearly 80% of apps removed from Android Market were free ones, Mikalajunaite said, which could mean that Android Market publishers put more effort into paid apps that will kept longer in the store.
The Windows Phone Marketplace had only 13% of its apps deactivated, but Mikalajunaite noted it is a comparably young store just being explored by developers.
Matt Hamblen covers mobile and wireless, smartphones and other handhelds, and wireless networking for Computerworld. Follow Matt on Twitter at @matthamblen, or subscribe to Matt's RSS feed . His e-mail address is email@example.com.