Bruno was German, they had many more liberties and rights than the Jews and the prisoners
Shmuel was a jew, he only had one dad and the German soldiers end up killing him, We has probably a very happy kid until the Germans captured him, the sad thing is that he was just only a little boy.
Bruno had many more things and his childhood was "natural" , he had a good house friends and a roof to sleep
Shmuels life wasnt easy at all every day was a struggle to fight for his life. He probably had friends but i dont believe you could really enjoy yourself in that enviornment. But Shmuel tried to make the best of his situation.
Bruno's curiosity led him to Shmuel , this led to Shmuel having a friend and some hope .
The best thing for them was: they were both kids they were curious and fun they had a friend to help them go through each of their situation. But most important they died trying to find Shmuels dad.