Hi, and welcome to Using English.
I think you will find that most people won't say one is "better" than the other. Aside from pronunciation, there are not very many things different between the two dialects -- or other dialects beyond just American and the UK.
The things that are different -- for example, some prepositions and vocabulary -- can still be understood by the other, so don't worry about it. Just read whatever you can and learn as much as you can, regardless of the dialect.
Student or Learner