I have enameled cookware pots and cast iron skillets. The enamel is over steel though, not iron. And it's wonderful for not having to worry about things sticking, and for easy clean up. But enamel over cast iron would be really heavy and I'd be worried about clean up issues, in case of small chips ever.
Cast iron can be easy to care for IME if you know how, which means seasoning it properly (or buy it pre-seasoned), never submersing in water, drying quickly, etc. But it can never be put in the dishwasher and so on. Enamel over steel, for instance, can.
And for nonstick, plain cast iron is a pain, I know, especially if you are on a lowfat type diet, because you need some kind of oil or butter to cook most things in regular cast iron.
The main reason we have cast iron at all is to help with iron/anemia issues, plus it was my grandmother's set, and I prefer it for making cornbread and pancakes, etc., in. But for everyday cooking, I far prefer my enamel stuff.