I had my (since replaced) Bosch dishwasher and KitchenAid washing machine repaired in the last year, and I asked the guy if he repaired certain brands more than others.

But the problem is sampling. Of course he fixes lots more GE and Kenmore appliances... because there are lots more of those out there than, say, Wolf or Viking or other high end brand. For example, he was certified to fix Fisher-Paykel dishwashers and laundry products but just because he'd rarely fixed them doesn't mean that they are repair-free.

So I didn't find it useful to ask the repair guy. Others' mileage may vary.