This applies in more fields than just programming. I've won a number of clients over the years based on the fact that most of my competitors (business strategy coaching / consulting) are 'one trick ponies'.

"How are you different to X?"

"My company has IP that addresses all 20 areas of business, and I work as part of a team so I can ship in a specialist if need be.

"X is great at following the bouncing ball to give you a marketing plan - if you have revenue issues, they will sell you a marketing plan; if you have culture issues, they will sell you a marketing plan; if you want to exit your business for the highest valuation in 2 years, they will sell you a marketing plan.

"When you only have a hammer, every problem looks like a nail. They only have a hammer, so you'll never be able to trust them when they diagnose your problem as a nail. A nail which needs a marketing plan."

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