I don't know if I agree with this. Fizzy drinks are filled with artificial sugar that the body converts to fat. Fruit is filled with natural sugars, that, in moderation, are of vital importance for the body. We buy our fruit and veggies by the bucketload and juice them, I find it the of the most efficient ways to get DS' fruit and veg intake up! The only downside to juice is the lack of fibre that comes from the pulp so you have to compensate for that. But I definitely don't think you can compare (proper) fruit/veg juice (not the crap on the shelves) with fizzy...
Fruit juice and soft drinks do contain roughly the same amount of sugar, with fruit juice though we naturally think that its fruit - therefore its ok because its "natural" but it will have the same effect on your teeth, and weight as soft drink... because sugar is sugar.
If you make your own juice how many pieces of fruit do you use to get 1 glass, its much better health wise and for your teeth to eat 1 or 2 pieces of fruit. I'm sure a glass of vegie juice with 1 piece of fruit added to the mix is a healthy option but if its all fruit the sugar level is very high.
In response to the OP I dont think kids should drink soft drink full stop... and I'm not a fan of juice either.