You should also post profile shots of their whole body. A lot of Silkie sexing is determined by the whole body stance. And we need to know the ages.
Having said that, I'll add, I am not a Silkie expert, so take my guesses with a grain of salt...
However, the top one has a pretty good walnut comb started, with a straight up pom, so may be a roo.
The bottom one has a big poofy pom, and may be a girl.
BUT...you would need to give ages and body profile photos to let the experts have a decent chance to guess.
Chicken A could possibly be a male but I have a few female silkies, full grown, that have a bigger combs than the others. I am 95% sure chicken B is a female but like as said in the first post, age is a factor you have to take in.