Most ServiceNow engagements need both consulting and implementation. A consulting-only engagement can leave an organization with a roadmap and no one to execute it. An implementation-only engagement can produce a technically sound build that solves the wrong problem, because no one assessed the business need before configuring the platform.
The overlap is where the value sits: a firm that can move from assessment to build without a handoff between two separate vendors. Consulting deliverables center on strategy, assessment, and roadmap work, and the output is a documented plan built by people with business analysis and platform strategy expertise.
Implementation deliverables center on configuration, deployment, and go-live work, and the output is a working ServiceNow instance built by people with technical configuration, development, and testing expertise. Consulting typically happens before or independent of a build, while implementation begins once the scope, whether it comes from that consulting phase or from internal requirements, is already defined.