A Mac specialist, and nothing else
This is criterion number one, by a wide margin. A Windows PC from another brand is not repaired at all the way a Mac is : the electronics, the fault logic, the tooling — everything is different. Repairing a Mac properly demands a brand specialist. Let’s be honest : even at Apple, the technicians don’t repair — they replace the faulty part. It’s an exchange approach, not a repair one. A true specialist, by contrast, works at component level.
The 30-second test : ask whether they repair only Macs, or other brands and other products too. Only entrust your machine to a pure specialist.