This is such a good question as they are both used in deliciously creamy rice dishes. Risotto rice is a starchy, short grained rice that releases the starch as it cooks (which is what gives risotto that oh-so-creamy consistency). Pudding rice is also a short grain starchy rice. However, where arborio rice tends to stay slightly firm in the centre, even after cooking (which stops risottos becoming mushy), pudding rice is designed to completely soften - which would give a rather different texture to this Courgette Risotto (Risotto di Zucchini). I suggest sticking with a risotto rice for this one and using your pudding rice to make a yummy rice pudding.