Huck is more practical and mature than Tom Sawyer. When Jim's freedom seems to hang in the balance, Tom insists on introducing many unnecessary elements into the escape plan. He chooses to play child's games, inflicting harm on others for his own fun.
Many critics have noted the thoughtless, even cruel nature of Tom's games, as they make Jim's life miserable and terrorize Aunt Sally.
Tom insists that Jim scratch ciphers onto a grindstone and write notes with his own blood on a stolen shirt though Jim is illiterate. Tom insists that Jim endure the presence of rats, snakes and spiders in his cell. These elements of the escape plan are pure fancy, designed only to satisfy Tom's idea of what an "adventure" should entail.
Neither Huck nor Jim approve of Tom's "adventures," although they feel compelled to submit to his authority in such matters.
These flights of fancy in Tom signify his immaturity. He does not realize or does not care than Jim is suffering through these ordeals and experiencing real pain.
Huck, oppositely, recognizes Jim's discomfort and relates to it. He continues to defer to Tom, however, for reasons that appear to be both moral and practical. It is in these areas precisely that we see Huck's superiority to Tom Sawyer.
Huck is mature enough to be willing to assume that others know more than he does and have authority where he does not. This is a wise humility completely lacking in Tom Sawyer. Huck also knows how to focus on a problem and solve it by the quickest means available.
This does not mean that he is always successful, but he is not self-serving in his failures as Tom often threatens to be.
I liked Tom Sawyer but he seemed rather stuck on himself by the end of the book. Apperently Tom is the mastermind of all things clever in the universe, or at least the one in the southern United States. Huck is different. His plans and motivations always seemed tinged with a slice of humanity. Huck, for example, truly liked the slave Jim. Huck made floating down the river with a black slave kind of cool! And how about those bad guys? Tom would have been all over their crazy scam. Huck knew it was hurting people and he scammed them! By the end of Huck Finn it is evident that Huck's heart is in the right place. He wants Jim free so he can have a shot at a real life. Tom helps free Jim because he felt it would be all hip and counter-culture to free a slave.