Deciding between two primary keywords

Hi

I am setting up a new site and have identified two keywords to focus on (which will then lead to other long-tail terms). But I would like to focus on one rather than both.

My question is, how do I choose? Let me give a made up example...

- Imagine I am a plumber

- Plumbing vs Plumber are the two main terms people use in various searches

- Where I am based, plumbing has 3x the volume of plumber

- However, plumber terms tend to have better intent for services

- In comparison, plumbing search terms are more often things like 'plumbing fittings'

- In ahrefs, Plumbing KD is about 60, plumber is 40

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How would you weigh all these things up to decide which to focus on?