That's a good point... though, I think the drama of isamu isn't necessarily how he changes, or even that he does, but how he allows the events in his life to change him. As for basra, it's the very fact that he doesn't change, and the reasons behind his views not explored that he's isn't an interesting character to me.
In the end, all I'm saying is that both plus and zero offer up good characterizations. Whether or not you or I happen to like the characters is something else entirely.