I am sure some British people have better pronunciation than some Americans and that some Americans have better pronunciation than some Britis. It is very subjective. If you are from a certain region and you go somewhere else you may not understand the way people pronounce things but to themn its right. I do not think that you can say certain people pronounce English better than others (assuming English is their first language).

Beeing neither, i think the Brits are better

British english has better pronounciation.

Brits of course - but only if you are speaking Queens english. Don't Americans speak American?

Americans are apparently easier to understand. I have taught English in foreign countries for 7 years and the students find the American accent clearer than the British. It's unfortunate as I'm English.

I don't think there's an easy answer. I lived in the States for many years and failed to lose my British accent (which seemed to delight American women who said "I just LOVE your accent - it's cute" - almost good enough to start chatting them up and even bedding them...while American men thought I was being pompous - I come from the South).

We have to remember that like all other aspects of language, pronunciation changes. (On both sides of the pond!!)

Whatever English-speaking country you're in, the regional form is considered the "best". One of my students is a Ghanaian, who (apparently) speaks English perfectly, but I often can't understand him - only after three or four attempts can I pick up what he's saying). Australians have their own variants, too. Americans laugh at Canadians when they speak, but then Noo Yawkers laugh at Virginians, don't they?
What about Ethnic English, then?

If you're in Britain, the British ways of speaking are more readily accepted. American companies advertising products in the UK often employ British speakers to dub their ads, rather than use the American originals.

As one of your respondents says, there are many varieties of British English (just as there are of American English in the USA), each accepted and indeed preferred in that area. Newsreaders in both the USA and the UK are more regional than ever (a tendency which began in the UK in the 60s, when "Northerners" became popular in many fields of entertainment - Beatles, Gerry and the Pacemakers, Kenneth Tynan, Alan Bennett, and the "posh" Received Pronunciation was beginning to decline), although our Cockney English is still not acceptable (at least by broadcasting companies) for serious programmes (news, etc..)

Some varieties of American English preserve regional features of old British English of 200 years ago.

A quick question for you: why do American women sound so harsh, shrill,raucous even? (Showing off? Or brought up that way?)
Why are black people so LOUD (when they see each other, especially when they laugh) Showing off again? Raising awareness?

Smashing! Jolly good! Toodlepip! (me being facetious.. fear not!)