Which level 7 creature is the best, and why?

They are all great! I tested them, and Archangel won 90% of its duels. I don't remember, I think it only lost to Behemoths. And it also loses to Archdevils on lava! About Dragons: if Gold had 275 Hit Points, it would crush Black, but as it is, it NEVER does. Although I usually take unbuffed Dragons with me; there are many advantages (resurrection), but there are also disadvantages, of course.