You want less sugar, eat a smaller amount. Fage single serve containers are bigger than Chobani and thus have more sugar.
The way to know what the naturally occuring amount is to check the plain yogurts that only list milk/cream and live active cultures for their ingredients. Fage 2% has 8g of sugar in 7oz. Chobani 2% has 4g sugar in 5.3oz. For both brands, they only have milk/cream & live active cultures in their plain yogurt.