There is no specific medical research over this matter. However, medical practice shows that most of pharm-grade brands have virtually the same effectiveness. The only exclusions are long-acting Darbepoetin (Aranesp) and NeoRecormon, made by Hoffmann–La Roche. Darbepoetin is more effective than others. Recormon is very convenient to use product of extremely quality – longer storage time, higher purity, etc. But if price matters, one can easily use other product line.
What is the difference between EPO Alfa, beta, etc.?
As it was mentioned above, effectiveness is mainly the same, but some people may be more resistant to particular product, i.e. one some people alfa may work better than beta and vice versa. Also, there are medical contradictions; certain types of EPO cannot be used with cancer, while they are better for kidney deceases.
So, when doing medical treatment, one should follow advices of doctor. For sportsmen it does not matter, which EPO brand to use, but keep in mind that personal reaction on certain EPO brand type might differ slightly. More expensive brands just makes it easier to use and less injection pain, but no more effectiveness (except darbepoetin)
Finally, at the moment (2013) we offer quite unique EPO brand, which comes not in liquid as most other brands but in powder. It should be diluted before usage, which makes it less convenient, but from the other hand it has longer storage time and better sustains transportation.