1, the genus is different
Black kidney beans are pterocarpus genus.
Black beans for the pteridophyte subfamily soybean.
2, nutritional value is not the same
Black beans are rich in vitamins, yolk, melanin and lecithin and other substances, including B vitamins and vitamin E content is very high.
Black beans are rich in protein, lecithin, fat and vitamins, but also melanin and niacin.
Black beans:
3, taste different
Black kidney beans are easier to stew, and very face, good taste.
Black beans taste similar to soybeans, harder; to stew longer to eat.
Baidu Encyclopedia - Black Beans
Baidu Encyclopedia - Black Kidney Beans