In the context of this problem, (2) makes more sense, because otherwise you may not even have the same features you are trying to classify (ie reduced dimensions may mean very different things). See here for a more detailed discussion http://stackoverflow.com/questions/10818718/principal-component-analysis

In the context of this problem, (2) makes more sense, because otherwise you may not even have the same features you are trying to classify (ie reduced dimensions may mean very different things). See here for a more detailed discussion https://stackoverflow.com/questions/10818718/principal-component-analysis