Similarities: They're both 9, both innocent and curious.They both have the same birthday which is cool and, in the movie have the same colored hair.
Differences: Shmuel is Jewish and Bruno is German-boy, Bruno lives in a nice home with fresh food and has an easy life while Shmuel is in a concentration camp, working him self to death and has no fresh food or clothes. and could die at any moment but Bruno is a lonely boy so when he hear Bruno say that he wishes he was there he probably thought that Bruno was stupid.
In the end, They are both kids from different countries, Shmuel being born in Poland by Jewish parents, And Bruno born in Germany and his father being a lieutenant for the Nazi Army.