Since Hamlet and Horatio were classmates at Wittenberg, besides that similarity, they are roughly the same age. They both are intelligent. One of the reasons Marcellus asked Horatio to witness seeing the ghost is because Horatio is a scholar (Act 1, sc. 1.) Hamlet's intelligence is shown throughout the play. Both Hamlet and Horatio tend to spout philosophically at times. Horatio tells us in the final scene of Act 5, than he would like to commit suicide like the ancient Romans did when a leader or a cause was lost. Hamlet gets philosophical many times in the play, especially in his soliloquies. The two differ in their philosophies however. Horatio is a stoic and as such, tries to display little emotion. Hamlet, on the other hand, is quite emotional. Hamlet seems to have little problem sending Rosencrantz and Guildenstern to their deaths (Act 5, sc. 2), but that Horatio even comments on it by saying "So Guildenstern and Rosencrantz go to't," indicates that he is slightly disapproving. Of course the two of them are also different in their stations in life. Hamlet is a prince and Horatio is not.