Microsoft’s digital assistant, Cortana, is one of the most impressive of its kind, outperforming its competition on an iPhone and a Moto X even in its early preview state. In fact, the early buzz surrounding Cortana has forced Microsoft to consider whether or not it would be worth bringing Cortana to more platforms in the future. “It’s a bit of a head-scratcher for us right now,” said Marcus Ash, a group program manager for Windows Phone, at the SMX Advanced conference in Seattle on Thursday. “It’s interesting to think about the future of these assistants and whether they become a reason to buy into the ecosystem. That is the other tension we have.” With Cortana eventually making its way to Windows PCs, Android