Simplicity FTW. The simple loop version is very easy to understand. It's probably really fast, as it's just a loop over seven items. And more importantly it's more correct. It doesn't use floating point arithmetic, so you don't have to worry about precision issues.

The logarithmic approach is harder to reason about, prone to bugs (as proven by this post). I'm baffled at the fact that tons of people considered it a more elegant solution! It's completely the opposite!