whatever you decide. I'm used to learn American English, but I have come to love British English. I like the way they talk, it really amazing to me. I feel good when I listen, and sometimes I have these dreams of myself speaking British English. But my Accent is more American than British. I will keep on learning American English, I have few miles to reach to the fluency. I won't start over and learn another accent now.
I am biased being English myself, but I think British English is a clearer accent and is often better understood. For example, I sometimes can't hear the difference between the words 'can' and 'can't' when a student is using an American pronunciation as they often swallow the final 't'. The difference in these two words is greater in the accent used in the south of England as the vowel sound changes. Having said that, as long as you learn good pronunciation of whichever accent you choose, you will communicate well and that, at the end of the day, is the most important thing :)