It's kind of a difficult thing to answer because there is a lot to consider and I don't believe there is actually one right correct answer.
With that said, I know there is a group of people that have used pharma that swear they can tell no difference. Then there's the group that have taken both and swear that pharma blows every generic out of the water. With that in mind, I have to agree with
@stone988 that if you notice better results with one of them... Then take that one. But I don't think either group can argue that one is better than the other.
Pharma probably gets a slight advantage because you probably aren't going to need to question it as much, whereas generics have a long history of being questioned. If you have a good source for pharma, you are probably all set... But the same argument could be made for generics. I think over time, they'll be seen as much more equal.. there's no question that they've been improving on tests even in just the last few years... I personally don't see a lot of bunk tests these days but I pay less attention to it because generics have treated me great. Consistently high IGF scores, great results too.
The last thing I think it's important to consider is, if you have a generic that's tested and it comes back the same as what a pharma product would... Then you have two generally equal substances. Even in the pharma world, I know several folks that prefer a certain brand over another because they say it's better... And I think it's the same in the generic world too. Personally, I always liked blacktops the best.
Sorry for the long winded reply that doesn't really offer anything concrete... TLDR is to just use what you get the best results from! If that's generics, great.. if that's pharm grade, that's okay too but I bet you'll use less of it.