Are smoothies made on just the frozen fruit and juice better than the one which adds yoghurt?

Actually, no. They'll be more balanced if you use yogurt as well, but if you're using full-fat yogurt, or a kind that's loaded with sugar, that will increase the caloric value significantly, so you'll want to stick to either sugar free or plain nonfat yogurt. The yogurt will offset the simple carbs in the fruit (which your body almost immediately stores as fat), slowing their digestion so your body can use them more effectively.