It's about the game that the two companies are playing. Google is playing, and Microsoft is not. (Here, one of the 16 "masterpieces" in the dogs playing poker series, from Wikipedia.)
With Google Android you see where all your competitors start from. You can innovate from there. You can differentiate your phone from other Android phones.
With Microsoft there is less wiggle room. The only people who see the code are Microsoft and (maybe) the manufacturer. You are betting that Microsoft can out-innovate Apple. (Stop laughing.)
No one in the mobile business throught Apple could out-innovate Apple back in the day. Remember when Apple was playing footsie with Motorola? No one in the mobile business thought Apple had what it took to be a "lead dog" -- they all wanted it in harness with an unchanging view.
So Apple did its own phone, its own way, and Apple won.
Microsoft lacks the courage to do this. It won't compete with its own ecosystem. It doesn't understand that hardware is software. So it plays the game the way Symbian did five years ago, even though Symbian has abandoned that game, so there is no reason to fear Microsoft, and no "there" there.
By contrast, think of Google as dealing hands of poker.
All the players at the Android table can see one anothers' cards. Not all the cards, but enough to get a feel for what's happening. They can keep their aces in the hole, they can innovate or compete in some other way.
The dealer is patient, you can play all day, and guess who ends up with most of the chips at the end of play?
Google is betting that carriers and manufacturers will play enough hands with it that it can gain some market share. Right now that looks like a pretty good bet.
Microsoft is like a gambler with a fistful of dollars that can't find the game.