That's a tough question! Certainly we have all heard of American English and British English, but consider Australian English, Canadian English, Indian English, and Nigerian English. I daresay there are probably at least half a dozen Englishes, which are the standards in the regions of the world where they are widely spoken.
Which English is Best?
Now that is another tough question! If English is your native language then the English that is native to you is best for you. Unless of course you create and consume content in another English. Then I guess you become bilingual in Version A English and Version B English.
However, if English is not your native language. then the English that is the most useful is the English that you are obliged to, or want to, interact with in the most. If you find yourself living in a foreign country where English is spoken probably adapting to the English of that country where you live is the most practical. That way you will be understood and can understand others there as well. Or perhaps you are based in your home country where English is not widely spoken, but you work remotely in the information technology industry, in English. Are you interacting with native English speakers in English? Are you interacting with non-native English speakers in English?
From A Recent Dialog with Karla
Nia: You will interact with people from all over the world, in English. There are many Englishes with different intonations, different word pronunciation, different vocabulary, different vocabulary usage, et cetera. You are having a great experience now because you are interacting, five days per week in English for 4 to 8 months at a time, with teams of people whose English is different from your English.
Karla: I agree. At first, it was very difficult for me to understand the people on my project. Now, I can understand them more when they speak and write.. Maybe for my clients my English is different and they must make a concerted effort to understand me, also.
I know English is very important for my work. I would like to communicate with other people very well.
Nia: Stick with the Standard American English that you are perfecting. Use Standard American English for your spoken and written output. Expand your comprehension of other Englishes through natural exposure. Don't hesitate to get clarification when what you are hearing or reading from your project participants isn't crystal clear for you. And even when you think you understand a request, statement or question, it doesn't hurt to rephrase it to let the other party know the communique you received.