I have read a couple of clinical studies on this. All forms of whey tested had essentially the same bioavailability. Whey isolate is purer than whey concentrate, for example. This doesn't change how quickly our bodies absorb the protein, only that the concentrate has more impurities (usually lactose and galactose sugars and casein protein). The only benefit of hydrolyzed whey would be for people who have difficulty digesting milk proteins.
This reminds me of a similar discussion about which types of sugar absorb more quickly. After reading the data, I can conclude that some monomer sugars do technically absorb faster than disaccharides, but we're talking seconds and not minutes.
The conclusion: timing and frequency of protein consumption are important. Go with what fits your budget, tastes good, and doesn't make you bloated.