The main difference between the two boys is that Huck is more of a realist and Tom is an idealist.
Tom is raised by his aunt Polly and Huck's father is a ussles drunk
If Huck is the consummate realist of the novel, Tom Sawyer is the representative romantic. From the moment you are first introduced to Tom, it's easy to recognize his role as a leader, or controlling agent, of the situation. The gang is labeled "Tom Sawyer's Gang" because he is the one that controls its activities and pursuits. These activities, however, are always based upon Tom's exaggerated notions of adventure. Basing his experience on the fanciful books he has read, Tom tries to adapt his life and the life of others to that which he has read. The end result is a parody of sensibility and emotion, two literary agents that Twain despised. Tom's role as a romantic is extremely important because of its contrast with Huck's literal approach. Although Tom declares that his gang will pursue the exploits of piracy and murder, in reality the gang succeeds in "charging down on hog-drovers and women in carts taking garden stuff to the market." The vision of the young boys disrupting women bound for the market provides much of the harmless humor during the early pages of Huck Finn, and Tom is largely responsible for the slapstick approach. Tom's constant barrage of exaggeration, however, contrasts with Huck's deadpan narration, and Huck can "see no profit" in Tom's methods. Where Huck is practical, Tom is emotional; where Huck is logical, Tom is extravagant. Despite the fact that you can easily recognize Tom's ideas as foolishness, Huck does not question Tom's authority. On the contrary, Huck believes that Tom's knowledge is above his own, and this includes Tom's attitude toward slavery.
