jms obviously can create complex, interesting characters, but I think Whedon is his superior in this regard. Case in point (I'm quoting one of the fine reviews of Entil2001):
Now, Babylon 5 is a big, complicated story, and we don't need to know the characters in such exquisite detail to appreciate it. Firefly is a much smaller, more intimate story, and characterization is the most important part of it. So I'd say jms and Whedon are both playing to their strengths.Perhaps because of his confrontation with Inara, Mal opens up to Saffron about his early years. As it turns out, Mal grew up on one of the settler worlds, which goes a long way towards explaining his sympathies for their plight and his anger at the Alliance. It also explains why he would fight so hard to preserve that way of life, and why he would see open space as a refuge. As with so many happier times, such things are usually left well hidden; one gets the feeling that the sense of loss would be too great.