If you are optimizing for making the current job take longer, then you should use a slower computer. However, if the reason people will pay you $150 per hour is because you are 10 times faster than the person who costs $50 per hour, you want to keep your speed as high as possible because that it what creates the long term demand for your services.
Most of my time is spent between the AWS console and VS Code writing Python and Node. A faster computer wouldn’t speed that up.