Have you ever made toffee? You take white sugar, and you heat it along with water for a time, and the color starts to change, starts to caramelize. The longer you "process" the sugar, the darker the final product gets (not to mention delicious!).
Though we don't recommend gnawing down on bamboo, the carbonization process of bamboo flooring works in a similar way. The strips of bamboo are boiled, heating and changing the properties of the sugar within the fibers. This produces a couple of reactions.
First, the main purpose of putting the raw material bamboo through the carbonization process is to attain different colors. The natural look of bamboo is a light tan/yellow, similar to straw. While beautiful in its own right, this color might not work for everyone's projects, so manufacturers apply this process to the bamboo in order to provide a range and selection of color to consumers, from just darker than natural to dark-mahogany-like depth of color. We do like our choices, don't we?
The not-so-great reaction that happens when bamboo is carbonized is that it loses strength. Think back to the toffee, the lighter the toffee, the chewier it is; the darker the toffee, the more brittle it becomes. Something similar can be said of the carbonization process effects on bamboo flooring. It actually loses up to a third of its strength.
This doesn't mean you'll be walking on marshmallows because the rest of the treatment of the flooring works to boost that strength back up (including applying an aluminum oxide finish), but it does impact where and how a floor should be used and how much traffic it can withstand and still stay beautiful. You also want to factor in whether your bamboo planks are strand-woven or "regular" planks. Strand bamboo is more expensive, but it is substantially stronger, even after going through the carbonization, because the fibers of the bamboo are actually woven together when assembled.
So whether you go with a light tone or very dark, you should be more than pleased with your new floor. And all this talk of candy…I'm off to snag something sweet!