You have folks in different groups with protein, very loyal and with adequate backup to their arguments.
You have the cheap crowd, because it is just that, cheap. Whey concentrates for instance...they normally max out at 80%
You have the isolate crowd, fast absorbing and cleaner so to speak of lactose(though this may be debateable)...more processing, max out at 90% or a bit more depending on the testing.
Hydrolosate crowd....super fast absorbtion. There isn't much protein left, its basically amino acids and some small peptides.
Then your slower absorbing proteins, milk protein, casein, etc.
And on....pick your crowd, and use it. A variety is probably best/allowing for your budget.