Android M, or Android 6.0 Marshmallow, is in the process of rolling out to Android handsets in the U.S., but Google's mobile OS is trailing behind Apple's latest iOS 9.1 update in a big way.

Apple's iOS 9 and Google's Android M started rolling out within weeks of eachother. But as of last week, Android 6.0 Marshmallow has only made it to about 0.3 percent of active Android handsets, according to Google's own numbers posted on the Android Developer Dashboard.

Meanwhile, Apple's iOS 9 had already surged to over 50 percent adoption in the first week it was made available in September. In mid-October, according to MacRumors, iOS 9 adoption had reached 61 percent of Apple's mobile devices.

And according to the latest figures from Apple as of Nov. 2, that wave of adoption is still going strong. Now about 66 percent of iOS devices run iOS 9, with a quarter of them running the previous version, iOS 8.

The figures take into account iOS 9.1, which Apple released about two weeks ago and which helped grow the overall iOS 9 adoption pool by about five percent. As it stands now, only nine percent of iOS users are running a version of the system software that's older than iOS 8.

In comparison, Android 5.0 Lollipop and its bug-fix update Android 5.1 both run a little more than 25 percent of Android devices. That number hasn't grown significantly in the last few months, as it was closer to 23 percent in September. Android 4.4 KitKat, now two years old, is the most dominant version of Android, with nearly 38 percent adoption across Android land.

Google can't really be faulted for the slow adoption of Android 6.0 Marshmallow, since carriers and manufacturers often customize the platform, thus slowing the update process down or preventing it entirely for some devices.

And Google and its partners noticed user frustration with slow updates, and in some cases have taken action: through close collaboration with Google, for example, HTC's latest One A9 handset promises to get Android updates within 15 days that they're released. Motorola similarly runs a nearly pure version of Android and has taken pains to update its handsets as soon as possible.

However, it's unlikely Google will ever win the mass OS adoption battle against Apple, which designs and manufactures every iOS device itself and takes pride in offering a consistent user experience on every device. Android is just too vast and too differentiated, by design, to ever beat Apple in the adoption race.