sweet potatoes are lower on gi. Baked are more starchy, but it really depends on how your body responds. Sweet potatoes are "said" to be better for cutting, baked for bulking, just listen to your body.
No matter if you're bulking or cutting, yams are the way to go. I've always used yams when I cut up or am training someone for a show. I don't use yams as much though for bulking b/c I get tired of eating them constantly.