It’s an old chestnut that pops up repeatedly. Which is the better version of English, the pure version of English, the genuine version of English – American English, or British English. I could write a book on the subject. But I have just a blog and only limited time and patience to give my opinions on the subject. There are differences, but essentially the variations are too few and too slight to make a difference. Which is my first response to any student learning the language with me. I suspect many of them want me to say British English, which through the British Council and others, seems to be pushed harder that its cousin from across the pond. This is largely because of a certain amount of resentment/antipathy and general ill feeling towards the nation across their northern border. Whereas there is some sort of romantic association with the UK.
American English has introduced many words to the language, although a lot of vocab that most people assume is of US origin is in fact British English – words that went with the waves of emigrants across the Atlantic and continue to be used there, whilst they have been replaced back in Blighty. Faucet is a good example. American English has gotten rid of some spelling anomolies that Brits persist with though. No ‘u’ in color, humor or favor.
There is no answer to the question regards purity though. Certainly in my opinion, although some have recently suggested Indian English has greatest claim to the notion. As for the differences. The greatest difference lies not in spelling, grammar or the core vocabulary, but in slang. As demonstrated by Hugh Laurie and his interviewer in the YouTube clip below.