You don't want to use a plumber that has scaled their business. That means that they're sending out a new hire to do your plumbing rather than the plumber that originally built the company's reputation.
The best plumbers spend $0 on advertising. They've got enough business through repeat customers and word of mouth to keep their small set of plumbers busy, and they're expanding slowly enough to properly train apprentices and ensure quality.
When I needed an emergency water heater I asked my boss who manages a few of his rental properties. When I needed a new roof I asked one of Facebook/Reddit/Nextdoor. I’d always favor word of mouth recommendations vs advertising.
The best plumbers spend $0 on advertising. They've got enough business through repeat customers and word of mouth to keep their small set of plumbers busy, and they're expanding slowly enough to properly train apprentices and ensure quality.