Tom is "old money". He takes his wealth for granted and expresses opinions that characterize him as bigoted and snobbish. Nick repeatedly describes Tom as a brute.
Gatsby is also athletic, sleek and handsome, but is not described with the same negative qualities Tom possesses. Gatsby is somewhat closed off, where Tom is blunt, gruff and too dumb not to be open. Gatsby is intelligent and secretive and he is a romantic.
Tom, like George Wilson, does not at all qualify as a romantic. He is not a dreamer and his love affairs are remarkably lacking in love. There is no poetry to Tom as there is to Gatsby.
George Wilson shares this dearth of poetry as well. He is trusting and easily beguiled. These qualities are used against him again and again, by Myrtle and then finally by Tom.
Where Gatsby and Tom have money, Wilson has bills. Where Gatsby works behind closed doors making surreptitious deals and Tom does not work at all, Wilson works where everyone can see him in his auto shop by the road.
1. Tom is crude; Gatsby is more refined. Though Tom has grown up with money, he is not refined nor is he gracious. Gatsby grew up with virtually nothing; however, though he is still rather socially inept and lacking in some niceties, he strives to be a courteous host and generally wants to please those around him.
2. Tom is overpowering; Gatsby is more reserved. Tom is a large man (with a voice that doesn't match his physical presence, by the way) and uses his presence to intimidate. Daisy calls him a brute and his mistress calls him "hulking" enough times to get a punch in the nose. Gatsby, on the other hand, is barely recognized at his own parties. He's shy and rather reclusive, and he is not an imposing presence--even when he wants to be, as in his confrontation with Tom in the hotel.
3. Tom was born with money and privilege; Gatsby engaged in shady business dealings to earn his fortune. They both treat their money pretty casually; however, Tom uses his to travel (usually when he has to get out of messy affairs) and please himself, while Gatsby sees money as the means to an end (to win Daisy, since that's why she couldn't marry him years ago).
4. Tom is a bigot (check his reading material and his views about it); Gatsby apparently makes few judgments about people (as can be seen in the array of party guests he entertains). The young Jay Gatz grew to disdain those whose sole motivation was money; however, as an adult he appears to be willing to overlook such things as he pursues his goal.
5. Tom has no purpose or direction in life other than to enjoy being rich and self-indulgent; Gatsby cares little for himself and is single-minded in his goal to win back the only woman he ever loved.
I'm doing an essay on Tom Vs. Gatsby -_-
Credit for this answer goes to auntlori who answered this in a similar question. hope it helps!