there are infact some substantial differences in the dialects, especially in the context of formalities. the european spanish tends to speak in the Usted -or formal, 1st person address- form more often. some nouns are different and of course the conjugations of the verbs will be different if you're speaking in the formal more often. -But- don't let that stop you from traveling to either local and trying to speak the language. you should be able to understand both, and you will learn to speak the particular way of the place that you're in quickly if you try. locals tend to be flattered, rather than put off, by your efforts. its an honor.