Comparisons: They were both sentenced by authorities of the law (Boo by a judge to the boy's school, Tom to jail), both treated unfairly (Tom by almost everyone, Boo by his father and brother), both misunderstood and misjudged, both key factors in the events surrounding the ending of the novel and Bob Ewell's attack, both key factors in teaching Jem and Scout about decency, morals, justice and humanity, both kind-hearted (Tom did work for Mayella often, Boo helped the kids out and befriended them), both were defended by Atticus (Tom literally with the trial, Boo when Atticus tries to protect Boo's privacy from the kids). Both of their innocent natures are symbolic of the mockingbird's song, and how it is a sin to shoot those birds.
Contrasts: Tom ended up being killed by a brutal society whereas Boo was just shunned by it. Tom actually received a sentence from a jury that was his punishment-along with society's racism, whereas Boo was a victim only of an overbearing and cruel father. Tom lived a normal life and Boo was a recluse.
Those are just a few ideas to get you started. Good luck!
Boo and Tom both share the distinction of being two of the adult, human "mockingbirds" in the novel. Both are harmless, innocent men who have been accused of terrible crimes which they did not commit. Public opinion deems them guilty nonetheless, and both men receive unjust punishment: Tom is found guilty of raping a white woman, and he is sent to prison to await his execution. Boo is guilty of a teenage prank, and he is sentenced to a life of confinement inside the family home by his father. Both of the men are damaged physically--Tom with his crippled arm and Boo from a lack of sunlight from being cooped up inside the Radley House--and emotionally: Tom attempts to escape from prison when he loses faith in white man's justice, and Boo eventually acquiesces to his family's sense of justice. Both men perform acts of kindness which are mistaken for evil: Tom attempts to help the friendless Mayella Ewell, who in turn accuses him of battery and rape. Boo leaves gifts in the knothole of the tree for Jem and Scout, but his brother, Nathan, seals the hiding place out of fear of Boo harming the children.
Boo Radley and Tom Robinson are both characters who can be connected to the symbol of the mockingbird. Mockingbirds don't hurt or pester anyone, which is why Atticus says it's a sin to shoot one. The theme behind this is that innocent people are like mockingbirds, especially those who are less fortunate than the majority. These innocent people should be allowed to live in peace just like mockingbirds should not be shot. However, this is not the case for these two men. Both Radley and Robinson are hounded by rumors, myths, and prejudices; consequently, they are treated with disrespect from the community. For example, Miss Stephanie Crawford spreads rumors that Boo Radley sneaks around town at night and looks into people's windows. Rather than minding their own business, or finding out the truth for themselves, people judge Boo Radley as a criminal or a boogieman.
Tom Robinson also has rumors spread about him by Bob Ewell. It's worse for Tom, though, because Bob Ewell not only ruins Tom's life by claiming that he raped his daughter, but when Tom goes to jail his family suffers for the rumor as well. Neither one of these men deserves the disrespectful treatment that they attract from the people of Maycomb because they are innocent men who haven't hurt anyone.
The differences between Boo and Tom are the following: Boo is white and Tom is black; Boo stays in his house but Tom goes out to work each day; Boo doesn't have a wife and children, but Tom does. They both have disabilities, but Boo's is social and mental whereas Tom's is physical because his arm is crippled. Boo receives better treatment from the community because he is white and has white family to watch out for him. On the other hand, Tom suffers from racial prejudices that Boo never experiences.
Harper Lee wants to look at more than just one kind of prejudice in her novel To Kill a Mockingbird. That's why she created the characters of Tom Robinson and Boo Radley.
The most obvious example of prejudice is the racism that boils up around the Tom Robinson case. Robinson, as a black man in the South, faces the same racial hatred that black people have had to endure there for hundreds of years. Sometimes this racism results in physical tragedy, even death, as with Robinson. But always it subjects the people involved (both the haters and the hated) to a diminished capacity to live their lives in a fully meaningful way.
With Boo Radley, we also see prejudice, but it is of a different nature. This is the prejudice that people engage in with their neighbors and other folks who aren't necessarily all that different from them. Boo Radley, and the other Radleys, were culturally similar to Scout's family and the rest of the white people of Maycomb County. But since they kept to themselves and lived in what seemed a peculiar way, they were subjected to unfounded speculation and character aspersions that were unjustified.
To Kill a Mockingbird doesn't ask readers to simply look at the cruel and unjust actions of others, which is all to easy to do; it also asks readers to consider their own potential unfair actions and judgments. Is there a Boo Radley in your neighborhood?
This is a good question. They are both innocent and kind. From a symbolic point of view, they are both mocking birds. This is to say that don't harm anyone and only do good. For example, Boo shows tremendous kindness towards Jem and Scout, and in the end he defends them from Bob Ewell. Tom, likewise, is kind towards Mayella. From this perspective they fit the definition that Ms. Maudie gives of mockingbirds:
“Your father’s right,” she said. “Mockingbirds don’t do one thing but make music for us to enjoy. They don’t eat up people’s gardens, don’t nest in corncribs, they don’t do one thing but sing their hearts out for us. That’s why it’s a sin to kill a mockingbird.”
They are also different. From the most basic point of view, one is black and the other is white. In book where the color of your skin matters, this is an important point. This is probably why Atticus was able to protect one and not the other. In this regard this book ends on a bittersweet note.