The hydrolized is better, on paper, but the benefits are small, and your body will probably not know the difference. It isn't signifigant enough that you would gain an extra ibs of muscle from using it post workout for a year. It has a faster absorbsion rate and a SLIGHTLY higher bioavailability. However, whey isolate absorbs at a rate that is more that adequite for getting enough amino acids into the bloodstream after training, if injested immediately.