This is interesting that Coke, Pepsi, and Red Bull all choose to sweeten beverages differently in each country. Apparently Mexicans have different tastes, as every blog post or message board I have seen contains posts from Americans and UK residents searching for Diet Coke because they find Coke Light to be undrinkable.
Interestingly, Red Bull is exactly the opposite. They choose to sweeten Mexican Red Bull with sucralose and aspartame instead of using the American combo of aspartame and Ace-K, which makes Mexican Red Bull Light taste sickly sweet to me.
PS After writing this, I learned that Coke Zero in the US uses the same sweeteners as Coke Light and tastes fantastic.