Chances are, if it's sweeter it has more carbs. I still count grape tomatoes as cherry tomatoes, though, because I rarely ever eat more than 4 or 5 in a salad. Just that few has more flavor than one entire store-bought, chemically-grown, red, round piece of cardboard they try to pass off as a tomato. (And yes, grape tomatoes have at least 5 times the flavor of cherry tomatoes. )

I've always wondered just exactly what the nutrient content of organically-grown heirloom varieties would be compared to the garbage they sell in stores. The vitamin count should probably be at least double, and my guess is there would be a few more carbs in most of it because of extra sweetness.