I personally feel that there's way too much emphasis put on this question of 'which English should I learn', anyway. The variants just aren't that much different.
It's often treated like it's as big a decision as choosing between say Chinese or French, when it isn't. It's not like there are any issues with mutual intelligibility between English variants. Even between 'extreme' (such as there are any extremes in English variants) variants such as say American and Jamaican English, it's still over 99% understandable.
Word stress may change a bit, idioms may vary a little, but English is still English. The problems you'll face learning the slight differences between variants are miniscule compared to the overall effort of learning English in general.
All variants are equally authentic, but I wouldn't consider them all equally as valuable to learn in terms of international communication. If you're learning English for business, then AmE and BrE are going to be the two major variants to learn. The choice between them largely depends upon where you're doing business.
Even if you somehow learned the "wrong" (from a business perspective) variant, it wouldn't prevent business ventures, and you wouldn't be starting over from scratch.
I speak American English. I could just as easily (from only a language perspective) start a business in the US, England, Mexico, Australia, India, Thailand, Turkey,Russia or any other country as could a colleague who speaks British, Australian, Indian, or Nigerian English. I could even partner up with one of those speakers to run a business together anyplace with no language barriers.