All things being equal, white wine tends to have slightly more sugar than red wine. However, concerning calories, many nutritional charts do not differentiate between them based on their sugar content. Both wines are listed as containing 25 calories per ounce.
While there is little difference in sugar content between red and white wines of the same variety, the amount of sugar in different types of wine can vary greatly. The fermentation process that creates wine from grape juice converts naturally occurring sugars into alcohol. Thus, wines that are not fermented as long retain more sugar and contain less alcohol.