According to the latest research from Nielsen, the high-profile launch of Apple’s iPhone 4S in the Fall had an enormous impact on the proportion of smartphone owners who chose an Apple iPhone.

Facebook and apps from Google like Gmail and the Android Market are the most popular smartphone apps among Android owners according to Nielsen’s latest research on smartphone usage.

NM Incite found that the iPhone has been the most frequently mentioned smartphone OS in terms of online buzz on blogs, message boards/groups, Twitter and Facebook, and online news posts, capturing 40 percent of online buzz about smartphones from July through December 2011.

In the U.S., 71% of those with smartphones own either an Android device or an iPhone. But when it comes to smartphone apps, iPhones and Android smartphones are even more dominant: 83 percent of app downloaders, that is, those who downloaded an app in the past 30 days, use iPhone or Android smartphones.

Nielsen’s third quarter survey of mobile users reveals that while only 43 percent of all US mobile phone subscribers own a smartphone, 62 percent of mobile adults aged 25-34 report owning smartphones. And among those 18-24 and 35-44 years old the smartphone penetration rate is hovering near 54 percent.

According to an August survey, 43 percent of all smartphone owners have an Android device. But if you ask only those who got a new smartphone in the past three months what kind of phone they chose, more than half (56%) will tell you they picked an Android device.

According to the first mobile media rankings based on audience measurement data from metered smartphone usage, aside from the Android Market app itself, Facebook, Google Maps and Gmail were the most used among U.S. Android users 18 years and older.

Forty percent of mobile consumers in the U.S. now have smartphones. Android is the most popular operating system, with 40 percent of mobile consumers reporting they have a smartphone with an Android OS. Apple’s iOS is in second place, with 28 percent.

According to first-reported data from Nielsen Smartphone Analytics, a new effort that tracks and analyzes data from on-device meters installed on thousands of iOS and Android smartphones, the average Android consumer in the U.S. spends 56 minutes per day actively interacting with web and apps on their phone.

According to Nielsen, Google’s Android operating system (OS) now claims the largest share of the U.S. consumer smartphone market with 39%. Apple’s iOS is in second place with 28%.