Numbers are compelling. They are objective and easy to remember. They improve the credibility and overall quality of your message.
A friend shared with me this LinkedIn post with writing guidelines that are adopted and promoted inside Amazon. While our boutique consulting practice is nothing close to the tech giant, there's a whole lot we can learn from it. Following these tips improve communication not only inside the company, but with clients and prospects.
The one that most caught my attention is the advice to be objective and avoid adjectives and adverbs. It's clearly the number one thing I need to improve in my writing (see what I did there?). Making a case is easy when you use numbers.

You can see how adjectives are imprecise and make it impossible to understand the magnitude of each statement. I'd even argue they are harmful, hurting the reader's ability to take decisions.
Whenever you can, include objective numbers in your communication.