An evolved Pokemon does better than a pre-evolved Pokemon by far, because it has stronger attack defense speed etc. However, some moves can only be learned by a Pokemon before an evolutionary stage such as quick attack which pikachu can learn but Raichu cannot. If you teach quick attack to a pikachu and then evolve it with its thunder-stone then your Raichu will know quick attack. You basicly just need to teach snorunt the right moves, THEN evolve it, and it will become far more powerful (Hence the stronger appearence). Hope I helped.