Good to hear you have had two hogs there!
Size isn’t a reliable way to tell male from female. Some mature females can be larger than some males. Although I have found the largest males tend to be larger than the largest females. But, as with humans, there is a bit of variation in size. Some hogs just don’t ever seem to get very big.
Having said that, my guess is that your resident hog is a female and the large one a male, from the behaviour you describe. I don’t normally take one incident as a reliable indicator, but females are the ones who normally make the huffing sound, and often move their little feet up and down in time – sometimes looking like a little jig – and usually reverse – usually when a male is around. However, if the male doesn’t show any interest, she may give up. Occasionally they start the jigging/huffing, initially, when a female arrives, but usually give up fairly quickly, once they realise. So it’s possible the large one could be a female. You’ll need to keep a look out and see if the behaviour continues or if he starts to circle round her – which is the start of male ‘courtship’ behaviour.
I have found that sometimes the large more mature males don’t always show too much interest in the very small females. (Maybe they know there is another more mature female near by and don’t want to waste their energy ‘courting’ a youngster – don’t know). But also if he is hungry, eating may take priority to ‘courting’. In my experience, certain males are always seem more interested in food!