Power architecture delivers more per watt
To reduce this discussion to simplistic terms: Power costs more than x86, but for the space and power used, it delivers more per watt. This didn't use to matter as much as being able to get a new piece of hardware at low cost on which to run an application. And indeed IBM makes no mention of Power's efficient energy consumption in this announcement. But in the cloud, space and power consumed matter. IBM is bidding for a bigger future for its Power archiectecture. Google is standing alongside it, for what purpose, I don't know. But it could be more than just some specialized big data handling.