I think you're probably really asking this:
"Whey protein concentrate and whey protein isolate - what's the difference and what do you prefer?"
Most of the cheaper whey proteins are mostly concentrate with a little isolate mixed in. The isolate is a higher quality protein, has less fat and lactose, and has a higher biological value. That being said, I don't see much of a difference when using them to justify the expense of a pure isolate. Optimum Nutrition's
100% Whey Protein Gold Standard works just fine for me, and for most everyone else I've talked to as well. The only reason you may want to go with a pure isolate is if you are lactose intolerant, as it does have less lactose (though it's still not lactose free). Hope this helps!
Train hard, Eat clean, Rest well. Make love 
