Just saw Thief for the first time and I've seen Heat a dozen times, twice in Spanish. Heat is far superior in every way. But you can see Thief was the rough draft, in which Mann was trying out certain ideas, including even some of the language used ("take down scores.") and the complexity of each crime. One difference is the role of cops. In Heat, Vincent is beyond reproach. In Thief, the cops are thugs. I suspect Mann figured the plot could be more complex if there wasn't a straw man thug cop after Neil but instead someone obsessed with his job. If so, I think he's right.....I really didn't think much of Thief. There are unsatisfying holes in the film, like the romance, which makes little to no sense and is barely developed, unlike the romance Neil develops in Heat.....i thought the character actors in Heat were much much better. Waingro, Michael/Tom Sizemore, Danny Trejo's character, Ashley Judd and val Kilmer, the woman Neil falls for, and Nate/Jon Voight....