imo Reservoir Dogs has the best dialogues from QT yet. When it comes to dialogues strictly, RD was the best, followed by PF and TR. Plus RD has the Whillelm Scream in it: way to transform a movie into golden !
For all these reasons, I love RD. True Romance is a lot of fun and it's just fantastic, but it doesn't top RD.
Though to really answer the question and be fair, we should compare the scripts...TR's is on dailyscript but I don't know where to find RD's one.
Edit: Ok found it! As I'm at work I got plenty of time to read it
That's sad I'm not under cover anymore : now you all know I'm a RD fanatic :O