Considering their relationships, who has the more modern marriage--Brutus and Porsha or Caesar and Calphurnia?

Well, neither is exactly modern, but in comparison, it would definitely be Brutus and Portia. The reason is that they are closer to a relationship of equals. For one, Brutus ultimately acquiesces to her demand to be told of the plot that is obviously bothering him. Even before that, it seems he does not because he wishes to spare her his torment, not because he thinks her unable to handle it. He wants to be "worthy of this noble wife." On the other hand, Calpurnia's attempt to be involved with Caesar's life, when she tells him of her dream, is blown off by a man who clearly thinks himself superior to his wife.