The difference in one line each
A speaker changes how a room thinks. The output is shared understanding across a large group, quickly, and it is measured in what people say to each other afterwards.
A consultant changes what an organisation does. The output is a recommendation about your situation, and it takes access to your business that an hour on a stage cannot include.
Signs you want a speaker
You have a large mixed audience and one hour. You want to open or close a programme. Your teams are anxious or sceptical about AI and you want the conversation reframed rather than answered. You want something people remember and repeat.
Signs you want a consultant
You have a specific decision with money attached. You need someone inside your data, your systems or your roadmap. You want a deliverable you can act on rather than a way of thinking.
The overlap, handled honestly
A workshop sits between the two: smaller, longer, hands-on, and it can end in decisions in a way a keynote cannot. It is the right answer more often than either party admits, and it is a format worth asking about.
What you should be wary of is a keynote sold as strategy. If a talk promises to tell your leadership team what to do about AI without anybody having looked at your business, that is a pitch with a stage under it.