There are big, brave guys in The Hobbit like Bard who seem to have no doubts about their courage or ability in this world. Bard represents the human armies of Lake-town, he directly confronts Thorin, and he fights hard during the Battle of Five Armies (in addition, of course, to shooting Smaug with a bow and arrow). So he's plenty brave. But consider Bilbo, whose greatest acts of courage are to face down Gollum in the goblin tunnels and to approach Smaug by himself in the Lonely Mountain. These are all acts that he does completely by himself, without fully knowing what he's even up against. While Bard's courage may be more open and recognizable, Bilbo's may take more actual bravery. After all, Bilbo is probably the least experienced and most vulnerable character in the whole novel, yet he's the one who is most willing to walk straight into the unknown by himself.