In the previous post we mentioned the growth of Android as a proxy for decisions to develop for the platform first (or exclusively). It’s no secret it has the greatest momentum and some research firms have already pegged it as the market share leader among mobile operating systems.

The latest is out from Nielsen, showing that Android has surpassed both iOS and previous market leader RIM for U.S. market share. Its ascent from a single digit market share last year is thanks to its open platform model. This is causing it to catch fire among OEMs and carriers (and users).

Interestingly, this is the opposite of iOS’s vertical integration strategy that Steve Jobs trumpeted during yesterday’s iPad2 unveiling. To his point, the melding of hardware and software under one roof has quality advantages. But it has scalability disadvantages compared with Android.

Android’s momentum will continue on the scalability afforded by unhinging software and hardware. This can be visualized in the graphic below. This is nothing new but a reminder that in some ways, it’s Apple vs. Microsoft (in PCs) all over again. This goes for mobile and will carry over to Tablets.