Iguana or cameleon? which are better pets?

Neither iguanas or chameleons are good begginer reptiles AT ALL. You should consider a gecko or a bearded dragon as your first reptile. Both are much more sociable and easier to tame too. A 45 gallon tank is not nearly big enough for an iguana, they need a 6 foot by 6 foot enclosure and a chameleon will not get enough fresh air in a tank, you need to buy a special, large, screen enclosure for a chameleon. Both have very complex dietary requirements. Check out anapsid for iguanas and flchams for chameleons. I urge you not to get either.