Well, Esperanto has the largest bases and the oldest and best functioning set or organizations speaking in its behalf. It also has the advantage of being almost familiar to speakers of most of the Western European languages. Of course, that latter is a disadvantage out of the area where those languages have sway.
The problem is that choosing Korean roots for an auxlang would not help Swahili speakers. So, the best solution keeps being to choose the roots that were more spread by colonialism, commerce, influence, etc. Of course, a lot of words from non-European origin ends up appearing anyway: chocolate, jaguar, tsunami, etc.
On the other hand, as the learners of artificial auxlangs would probably be idealistic people at most, having a mix of roots from all continents and "races" might be a point in favor of an auxlang.
Anyway, it seems that English is the current de facto auxlang, although it's not the English of native anglophones, as English proper pronunciation is very hard to get. It's rather a simplified English with such a mix of pronunciations that makes face-to-face communication a little hard. I was recently in an international conference and I witnessed how the English spoken by some Japaneses and Italians can sound very different from what natives speak.