As we examine this question, it's important to recognize how the roles of both the CTO and the CIO are changing.
In many enterprise organizations, CTOs are responsible for setting technology strategies and establishing standards while ensuring that technology that's used by the business adheres to those criteria. Meanwhile, CIOs are accountable for working with business and functional leaders to set business strategy and to make sure that the IT organization is aligned in meeting the needs and expectations of the business.
As mentioned before, the roles of both the CTO and the CIO are changing. As enterprises increasingly make use of cloud and SaaS-based capabilities, CTOs find themselves attempting to mesh cloud architectures with the organization's IT architecture that they've helped construct. Meanwhile, CIOs who have earned a seat at the table with other business leaders and CXOs are increasingly taking on added operational responsibilities including facilities management, procurement and supply-chain management.
There aren't cut-and-dried definitions for the roles of the CTO and the CIO since they vary from one organization to the next as well as by company size and industry. In some cases, there's a single IT leader who effectively handles both roles. This further complicates the discussion.
As cloud computing becomes more pervasive, some pundits have suggested that the role of the CIO may disappear entirely, with the CTO becoming the top IT dog as an overseer of strategy and standards. On the other hand, some CIOs have positioned themselves as vital entrepreneurial leaders where they're helping their companies to identify and act upon opportunities for leveraging emerging technologies to help the business establish unique market positioning.
Both roles are strategic and both are critical in helping the business to meet its objectives. I don't know the answer to this question. But with the dramatic changes that continue to occur both in the market and in the roles and responsibilities of CTOs and CIOs, it's a subject that's worth considering.