Nintendo said Thursday that it would release a new model of its DSi portable game platform with larger screens and built-in software.

Following aNikkei Shimbun report on Tuesday that sketched out the basic details of the platform, Nintendo made it official this morning alongside its Q2 financial results: The new hardware will be called Nintendo DSi XL, or Nintendo DSi LL in Japan.

Going against the trend of micro-sizing portable hardware, the DSi XL will be significantly larger than the current model (see the size comparison below). It will feature 4.2″ screens, which Nintendo says are 93% larger than the current models’.

It will be available on November 21 in Japan, and in the first quarter of 2010 in the U.S. and Europe.

While the XL will include a normal-sized stylus that slides into the unit when not in use, it will also include a much larger, more comfortable touch pen.

Nintendo also said that the Japanese version of DSi XL will include built-in software. Besides the DSi Browser and Moving Memo software, it will include both of the downloadable Brain Training apps that are already on the downloadable DSiWare service, as well as a new dictionary application.

The larger size will also come with a larger battery. Nintendo says that DSi XL will get from 4-5 hours of battery life on the brightest screen setting, or about one more hour than the DSi.

On the lowest setting, users can expect 13-17 hours from the XL versus DSi’s 9-14, Nintendo said.

XL will ship in three subdued colors: Natural White, Deep Brown, and Wine Red (pictured).

All these features support Nikkei’s two conclusions about the target market of the DSi XL: It is meant to entice older consumers into the fold, and to compete more directly with the iPod Touch.

Whether this helps Nintendo expand its audience again or is simply looked upon as a Game Boy Micro-style misfire (but in reverse), I don’t know.