Beatty and Montag are similar and different in various ways.
First, they share the same vocation, at least at the beginning, and have worked in the book-burning business for a long time: Montag for ten years, Beatty for much longer. Second, they both have/have had an interest in books; it is hinted that Beatty has read extensively, and he can manipulate others with his words, while Montag's interest is still growing.
Their differences are more pronounced. Montag is changing throughout the book, developing a sense of personal identity, leaving the society behind. Beatty is not the same as others in society, but works hard to present a facade of normalcy; he is much smarter and more individualistic than most, but he conceals this in order to do his job better.
"I've had to read a few in my time, to know what I was about, and the books say nothing! Nothing you can teach or believe."
(Bradbury, Fahrenheit 451, Google Books)
Montag, although he does not yet fully understand the things he reads, knows that they are important and worthwhile; Beatty considers them useless and meant only to cause discord. Beatty also uses literary phrases and ideas to manipulate people, while Montag, without the background, operates more on emotional response.
Beatty and Montag are both firemen. Beatty read books before and didn't like them at all. Now Montag is starting to read books he wants to keep learning and wants to keep the books to where they aren't gonna get burnt.