It's more of a personality trait that a "role". A typical CTO in a small organization is less of a people person and more of a technologist, the VPE is more of a business process person (it needs to ship on tuesday, don't forget the customer). As organizations upside into big entities that role separation still exists, where the VPE is very much management (performance reviews, schedules, budgets) and the CTO is now more front facing but still more focused on the technologies/industry than the process.