Plumbing searches come in two kinds. There's the emergency, a burst pipe, a backed-up drain, no hot water, where someone calls the first credible name on the map. And there's the planned job, a water heater replacement or a repipe, where they compare reviews and prices first.
For the urgent ones, where the customer is standing decides a lot. A plumber can dominate the map around the shop and be missing on the far side of town, which is exactly where a company that drives to its customers needs to be seen. Paid Local Services ads often sit above the map for these searches too; this doesn't touch ads, it works on the free listings beneath them.
What tips the call is usually reviews that mention speed and honesty, a working phone number, and a profile that says plainly which jobs you do and where.