I have always been using generics and they have seemed to work. There have been several brands but when looking at the manufacturer info on the package, they all have been made by the same company in Portugal. I have been on TRT for years and get labs that reflect the dose I took.
I did get one bad vial over 10 years ago. My T very low. I reported it and the manufacturer checked the lot and said the vial they had was still good. Anyway, other than that one incident, generics have been fine for me.