It's too early to compare Justine's comeback to anyone's, Miami was only her first tournament in seven months. She will get better by the time Roland Garros comes.
Kim is probably a huge favorite for the clay season, though she said she would be glad when it's over because it takes so much from her body, especially her wrist(!?)... Well, good luck to the belgians and to the Williams, I think the four of them will do well, and I'm sure Justine and Kim will win at least one title each. I don't know about Serena, she is good on clay, but it's clearly her worst (or less good) surface, so if she faces Justine or maybe even Kim, she might lose (depending on the previous forms).
Proud member of Justine's Philistines Society™
"There's a bit of Justine in all of us"