How do whey concentrate and isolate differ?

They are different forms of whey protein ingredients. Compare the finished product label: its protein, fat and carbohydrate content depends on the specific blend.

Do not assume every product shares all the properties of its base ingredient. Flavours, cocoa and mixed protein sources can change the final nutrition values.

Compare equal amounts, such as 100 g, then your preferred serving. If you need a lactose-free product, check for a separate manufacturer statement.