I book a couple of awards between SGN & IAH each year. My favorite is LH to FRA & TG to BKK onto VN. Lie flat all the way to BKK. It's a bit longer, but I find that I sleep better & that jetlag is not quite as excruciating.
Between BR & OZ I'd pick BR. 3 hours in Y I can handle. Angled seats just put me in a bad mood.
Just my experience.