Objectively: in a way that is not influenced by personal feelings or opinions.
''examples I can bring up, all of which I have encountered personally''
Note I said it depends on the drug. Now (I'm quoting here) 'Generic drugs are required to have the same active ingredient, strength, dosage form, and route of administration as the brand name product. Generic drugs do not need to contain the same inactive ingredients as the brand name'.
So, as per my example above, if I want to buy a 200mg Neurofen tablet (or a strip of them) I can pay £3 for a box of brand name or I can pay £1.00 for a supermarket generic version.
There's a consumer company over here called 'Which'. For years it's tested and compared products. One such test compared a bunch of brand name Neurofen products. All made by the same company but one was for neck pain, one for back pain and so on. Every one tested out as the same. No difference what so ever. Then we have newspaper reports of generic vs brand and (again as above) IF the ingredients were identical in every way there was no difference except in price.
You yourself say 'Basically, the great majority of the raws come from China, so all companies end up with the same product. But then the differences come into place when some companies filter and clean these raws more thoroughly than others.'
Objectivity needs to be what it said it is. Even in your dads example science argues that a one off result doesn't prove a theory.
To be clear - in the argument of branded vs generic - you must compare like with like. If there are missing or added ingredients, if the active ingredients are different in amounts or form then you are NOT comparing like with like. Where the above is identical in every way you pay a higher price for the branded name and or perception of value.
Regarding perception of value over actual value. It's a very, very simple trick. I can take two identical products - made to the same quality in every way. I sell one on street corners in a plain brown box dressed casually. The other I put on a white coat, stick a pen in my pocket and maybe add a stethoscope. I also make the box a white one. And instead I sell it in a store. Guess which one people trust the most?