They have certified mechanics to properly diagnose your problem
Will show you the broken/worn/defective parts
Doesn't price gouge or mark up parts they have to order
Can complete the repairs in a timely manner
I personally suggest befriending one of the techs and asking do they do 'side work'. Same skillset, same tools (for the most part) much lower cost. Most of them are glad to make $$$ 'under the table'.