Please do not accuse Cambridge of possessing a weak English skill, since Cambridge is a prestige university with high reputation in the English sector.. Instead, blame Cambridge centers Malaysian branch. Do not compare them, since both of the examinations are the same, the ESOL you take in the British Council is from Cambridge International Examinations, which is a sector of Cambridge. Even the CIE A levels provided these are of Edexcel and Cambridge.. You can only compare the faculties and teachers. The teachers at Cambridge centers are hired Malaysians, therefore, still possessing Malaysian style of English and their regular procrastination. In addition, the fact that they're part timers indicates that's not their main pot of rice, so they don't need to work extra hard.
While in British Council, the teachers are hired from English speaking countries, whose native language is English. Even if they're losers back then, they'll still be professionals here because English's their first language. Therefore, their teaching is much much better.
However, if you're just pursuing the recognition of the certificates, both are the same no matter where you take your examinations, because every sites will eventually report the scores back to Cambridge for evaluation. Please do some research.