Which brand of English dictionaries is the best one?

If you need to look up the pronunciation of a word in a dictionary, then the differences between an east and west coast accent are the least of your problems. IPA symbols are fine if you need to know how to pronounce words in languages that you do not already speak, e.g "бязательно"(Russian), "時間" (Chinese) or "écureuil" (French), but you do not NEED all the complex symbols used in the IPA system when a more simple watered down system directed to the target language is already available.

''If you need to look up the pronunciation of a word in a dictionary, then the differences between an east and west coast accent are the least of your problems.''

I don't think so. A learner should stick to just one accent and not use a mixture of various accents (a mix of LA&NYC accents or a mix of Glasgow and Bristol accents)...