This is easy! Americans use an American accent, and British use a British accent. However most people around the world who try to learn English as a second language actually fail to perfect a natural (native-like) accent and instead use heavily-accented English with strong traces of their native language being evident. So, maybe you should instead be asking, which English is more suitable for you, American English or British English? And the answer to that question really depends on where you go and what you need to use English for. It is worth noting that in spite of the differences between American and British English, at an academic level the two forms of the language are extremely similar. Ultimately, English is English, and if you speak it well you will be understood anywhere in the English-speaking world.

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?

The term American accent may be a bit deceptive. If you mean the accent used by Americans you hear on TV and radio, I would think that about 200 million (out of 330 million) people in the US speak like that. However, about one third of the American population lives in the southern area and speak with a southern "drawl". The southern accent is as different from the normal American accent as the British accent is.

That is a tough one. You might as well try searching it on the Internet. All the people answering the question will do the same :D As per my opinion, British accent is limited to a small geographical spread whereas American accent is very widely spoken. In absolute percentages, I could not find any reliable source of data :D

yeah American accent is much popular then British, its nearabout 80% american and 20% british