I see the initial question of this discussion as being wrong, there is no single "best" kind of iron.
Too bad, when people get osteoporosis, they think "ooo, I can take more calcium and it will fix it". Similarly, when people are anemic they think "oooo, I can take more iron and it will fix it." Osteoporosis and anemia are not caused by lack of calcium or iron. I use these as being exemplary only.
To fix osteoporosis or anemia would be even farther divergent from the topic of this forum. But the answer to the original poster's wayy off-topic question is: "There is no single best kind or iron" Isn't it funny the variety of responses received ? Wow. People must have wayyy too much time on their hands