The main difference between whey concentrate and isolate is the processing.
Whey protein isolate undergoes more processing in order to isolate the protein from whey.
The processing to isolate the protein component of whey, clears out a lot of lactose, fats, immunoglobulins, vitamins and minerals.
This is why a 20 gram serving of whey protein isolate will contain around 18 grams of protein, whereas a 20 gram serving of whey protein concentrate will contain on average about 16.5-17 grams of protein.
The flavor profile of whey protein isolate is also more easily manipulated via removal of the other components of whey, making it much more amenable to use in processed foods.
Whey protein isolate by itself will be less flavorful.
The more processing that occurs with any food, the greater the loss of its inherent nutrients.
Often words like protein are thrown around, like protein is protein and it is all the same, just hit your gram levels. But just like 20 grams of protein from black beans is not going to have the same benefit as 20 grams of protein from beef, so too, when it comes to whey protein isolate as compared to whey protein concentrate.