5 - She will be the undisputed face of Bellator and would not have to exist in Ronda Rousey's shadow.
4 - She can make demands or requests of Bellator that would be unheard of with the UFC.
3 - She would not have to immediately fight Ronda Rousey.
2 - She would help create credible competition with the UFC for female fighters, which is never a bad thing for fighters or fans.
1 - Signing with Bellator would not necessarily eliminate the chance that she could still end up fighting Ronda Rousey. If Carano were to win her fights at Bellator, she could still conceivably set up a one fight champion vs champion against Rousey with a much stronger say in the earnings from such a superfight.