There is not one British accent and one American accent, so it's impossible to have a preference. https://en.wikipedia.org/wiki/Regional_accents_of_English#Great_Britain

The british of course. It's royal english, understandable enough for everyone, even for americans, and it sounds clear and correct. In my opinion it is better to speak with british accent than american .

English accent

American accent is easier to understand for non-native speakers.

hello ,haw are u ramadan karim