Yup, there is only one kcal difference between them. I keep getting this question when I teach, as the aspartame scare in Sweden has increased a lot after a book called ‘The secret chef’ (In Swedish ‘den hemliga kocken’) was published. But, the way I see it, if you drink alcohol, smoke, don’t exercise, eat candy, chips, fast food, stress a lot and so on, if you do one or two of these things, then you need to reconsider your focus. The things I just mentioned are proven to negatively affect your health, whilst consuming aspartame is not. So, why don’t you do those things first, and since drinking sodas (light or not) don’t do anything for your health you probably should keep the intake down anyway, aspartame or not. Pick your battles, and pick them wisely!