For most of us we only buy a given part once, or at least that is the plan

. That means our "experience to compare quality" is pretty limited. Now Tony, a.k.a. 4-5-6 Chevy Trucks, has been buying parts for years, and the same parts over and over since he restores 4-5-6 trucks.
I'de say his advice is gold, purely based on the principal of "been there and done that".
Might be best to ask about specific parts, and then get the advice on who is best for that part.
For what it's worth I personally like Classic Parts of America and The Truck Shop, LMC is always last on my list.