They are both as accurate. That's not the point, though. The metric one is more natural; why do we count in base 10 ? Why not 16, or octal ? Simple, because we have 10 fingers. BKS nailed it right; it is much more natural to use a system based on the powers of ten, because that's what our entire arithmetic is based on.
There is also another argument, which is that it is easier to express things in metric, for the same reason; and people prefer shortcuts.

As for the "it keeps your brain active" argument, please. I sure hope that was a joke.
If we get to the point that that's what we rely on to keep our brain active, then we've got serious problems.