The simple answer is that there is not as much difference as you would think. Here's a situation. Imagine listening to a discussion between two business experts, one from London and one from New York, or two academics, one from Oxford and one from Harvard. There will actually be very little difference in the way that the two people speak. The GA speaker will pronounce the 'r' sound at the ends of words such as 'far' while the RP speaker will probably not. There will be certain differences in the way that some vowels are pronounced, particularly 'o' and 'a', and slightly different realisations of 't' and 'd', for example. There may be occasional stress pattern differences in one or two words. And that's about it. Otherwise, the two people will speak in a remarkably similar way. And I can guarantee that the average Chinese person would not be able to tell you which person was American and which was British. In fact, there are more differences WITHIN English-speaking countries than between them. A Texas farmer will sound very, very different from New York taxi driver. Likewise, if were to record working-class British people talking in pubs in London, Liverpool and Glasgow, they would sound so different from each other that you would not believe that these people were even speaking the same language. Obviously, in your case, you would not want to model your pronunciation on either the Texas farmer or the Liverpool dock-worker! Your aim would be for a neutral, standard, educated accent, and it really doesn't matter whether you model yourself on the Harvard academic or the Oxford one - the differences are minimal. And, needless to say, both are equally acceptable wherever you are in the world.

RP is the standard "British" pronunciation, while GA is standard American. RP could be considered the prestige pronunciation in UK English (including Australian and South African), while GA is a neutral American. In reality, most British speakers do not use RP. RP and GA both have their origins in Southern England, so they're actually relatively similar. On the other hand, if you chose a local pronunciation from, say, Northern England, that would be far less useful outside of the region in question.

Hi Lawrence, The "better choice" is up to you. Which form of English are you aiming to learn? If you want to learn American English, then certainly General American is the pronunciation you should be aiming for. However, if American English is not your goal, then there's no need to worry about General American pronunciations. Just to let you know: I do have American English pronunciation lessons on my teacher page if you're interested. Feel free to check them out.

@Kelly: thank your comment here.

From what I understand, GA and RP are 2 different phonetic realizations. GA is understood like American accent while RP is understood like British accent. There are some differences between American pronunciations and British pronunciations, such as in "a" sound as in chance, man,... or in "o" sound as in hot, spot, ... or in "ou" sound as in show, snow or the way Americans pronounce "t" as "d" with soft t as in computer, hospital, ... It is hard to explain full details for you, but if you can look up some video on the internet or youtube about differences between AC and BC, you will find many videos which show clearly all details with examples. Both accents are good and it does not matter what accent you are speaking with as long as you are understood, so it's up to you to choose one of them to imitate or some people speak pronounce words with both ways. I think AC sounds cool while BC sounds hot, but It is easier for me to imitate ways Americans pronounce words because I have watched so many American shows.