This is an interesting article looking into what affects the nutrient content of tomatoes. Organic tomatoes are higher in some nutrients, and size does matter!
"So, a little stress can be a good thing, and too much of good things like nitrogen and water can become a bad thing for farmers wanting to produce nutrient-dense food. For consumers hoping to choose organic (or conventional) fruit with relatively high nutrient levels, look for fruit that is small to moderate in size. And don’t forget the icing on this cake – smaller, more nutrient dense fruits and vegetables are almost always tastier.