I don't see why you wouldn't understand. Taking a bigger turbo and a smaller turbo, though, both the same in similarity, are still like comparing apples and oranges. What A/R do they have, how big is the inducer and exducer, what is the exhaust housing size? blah blah blah, there are a lot of factors. If you feed the same amount of pressure into these turbos, with specifications being different, there are going to be different variables as a result.