The pros of the situation are: more people supporting the conspirators' plans,
less people supporting Caesar's monarchy, and potential help along the way because of people wanting to aid in the plans. The cons of the situation are: Caesar can find out about the plans easier with the more common people in the know about the conspirator's plans; especially if a strong believer in Caesar's monarchy finds out about the plot and reports it back to Caesar.
The pros out way the cons in this situation because the people are blinded by Caesar's "greatness", and Brutus joining the conspirators and shedding light on what is actually happening to Rome is what the people need in order to stand up to Caesar rather than worshipping him as a god. Brutus cares about the people too much to not give the plans his best effort and make sure that everything is planned and thought out with great detail. This is not as much of a factor with the other conspirators as they want Caesar out of his position based mostly off of jealousy.