Neither of them, but Alphabet will be better positioned than Microsoft.

Big corporations don't adapt well to novelties. They can't handle what Clayton Christensen called "disrupting innovations" in his book The Innovator's Dilemma. Microsoft is already showing this in how they tried to enter the smart phones market and failed miserably.

Alphabet came into being one technology generation later than Microsoft, that's why they stand a slightly better chance to survive, but don't count too much on that.

The corporate giant who will dominate the AI world doesn't exist yet. There may be a guy or two working in a garage to create that giant, it's too early to tell.