It's more difficult by the advent of substitutions in Intgration (differentiation is practically nonexistant past Year 11 except as a basic tool like adding/subtracting). Basically you can't integrate straight away, you have to change the form and fiddle with it till you get something that works. That's the basis of 3U substitutions, however they tell you what substitution to use. 4U they don't, plus they teach you a whole host of techniques of integrating which you don't need in 3U as you never get questions like them.