I always looked at it like Heat is a sequel to Thief.

Personally, I have always preferred THIEF to HEAT. While HEAT is a fine film, it always felt a bit clunky to me. Vincent's wife/stepdaughter drama was clumsily handled and makes him look like a buffoon (three marriages? You'd think he'd wise up after the first).
While personal preferences are fine, you might have missed the whole point of Hanna being married three times and not "wising up". Vincent, just like McCauley, is someone who inadvertently sacrifices personal life for work. This makes them two sides of one coin - two proffesionals following strict code of rules that are ultimately destructive.
THIEF, however, doesn't have any problems that I can see. Mann's finest offering, I say.
It's "Heat" for me, but "Thief" is pretty close, along with "Manhunter" and "Insider". Mann's such a great film-maker.
Do you have any tobacco?

Yeah I've always preferred Thief to Heat as well really, I think Heat is over rated, I always have done.

Personally, I have always preferred THIEF to HEAT. While HEAT is a fine film, it always felt a bit clunky to me. Vincent's wife/stepdaughter drama was clumsily handled and makes him look like a buffoon (three marriages? You'd think he'd wise up after the first). Also, that final foot chase/duel in the airport is poorly handled. No amount of suspension of disbelief keeps me from noticing that Pacino and De Niro weren't on set together that day (any 2-shot in that scene contains one stand-in).
THIEF, however, doesn't have any problems that I can see. Mann's finest offering, I say.