They look the same size, so they should be the same sex (males are much larger). My guess is that they're female, the males I've seen have all had more caruncles on their face.
If they're female they should lay eggs occasionally, though!
Mine are a landrace! "Svensk myskanka", which means "Swedish muscovy duck". I live in Sweden so it's very fitting.
And there's a muscovy hen in the below picture as well... Let's see if you can find her.