They both look black on my screen! Can't tell very well with these pictures. They both look like they have small combs so I would be leaning towards pullets at this stage. However some silkies are later bloomers than others. One of them has a single comb, this is not desirable in this breed.
If they are sup to have walnut combs how did they get the single combs? 2 of my silkies has a single comb which doesn't bother me they are just pets anyway but I was curious. On one of mine it looks like he has 3 rows of combs.
And that's why it's really harder for me to tell the sex of black silkies from a picture. I can't really see anything but black with these guys.