Read over the scenes between both couples - Brutus and Portia's conversation is in Act II, Scene i, and Caesar and Calpurnia's conversation is in Act II, Scene ii. You can also look for line-by-line "modern" translations of the scene online (google or such) to aid in your understanding if you have difficulty with the language.
To compare, look at the fact that both wives are trying to convince their husbands to do something - Portia is trying to convince Brutus to confide in her, and Calpurnia is trying to get Caesar to remain at home for the day. Look for other similarities in how the women talk to their husbands - they both are meek and appeal to their husband's love, etc.
To contrast, examine the husband's reactions to their wives and also the reasons the wives give to appeal to their husband's feelings. Portia appeals to her faithfulness as a wife and tries to make Brutus feel guilty about not "trusting" her. Calpurnia says a dream warned her Caesar should not go out.
- both the couples having the different oppinion both the wifes are convience their husband portia is trying to convuece brutus calpurnia is trying to get caesar to remain at home at the ides of march because of her bad omens