From a translation website http://www.your-translations.com (not sure how accurate the following is): "British English is dominant in the U.K. and in some of its old colonies (such as Australia and Canada), but overall, it makes no doubt [sic] that, if there is such a thing as a “Universal English,” that would be American English. According to these figures, American English represents an astounding 80% of the English-speaking Internet. When in doubt, you can't really go wrong with U.S. English."
However, I usually recommend to students who are going to do a lot of business in Europe to study British English. If you are coming to the United States or Canada, then study North American English. And if you are going to Australia or New Zealand, then study their variety of English. It's important to ask yourself: How are you going to use your English, and with whom?