It sounds as if you have started your own research into the similarities and differences between these characters. Have considered these?
- Brutus and Cassius both have taken note of Caesar's growing power and don't like what they see.
- Both command armies after Caesar's assassination.
- Both are capable of deception, political intrigue, and murder.
- Both choose suicide over capture.
- Brutus acts out of a sense of responsibility for Rome; Cassius seeks power and position for himself.
- Brutus is trusting; Cassius is manipulative.
- Brutus is naive; Cassius is cynical.
- Brutus is an idealist; Cassius is a pragmatist.
- Brutus does not abuse power; Cassius does.
There are some other differences that are developed in the relationships these two have with others. Brutus, for example, has a wife whom he loves and tries to shield. Portia's death is devastating for him. Cassius, however, seems to love no one. His sole focus remains upon himself, the wrongs he has endured at Caesar's hands and the prominence he feels he is due.