I can't speak for every one, but if I mention a specific branded product, there is typically something that I like about it versus others that I want to make sure that specific one gets used.
Now the difference(s) may be real or it may all just be in my head, I could care less about which one it is. If I don't have a preference, then it's just the more generic product type, just so long as that type is used.
Sometimes it's just marketing, sometimes there might be something else that makes me like one over the others (it may be right or it may be wrong).
That's just my take on it anyway.