I looked up some pictures and this is what I've got to say,
Try and find pictures of wyandotte pullets and cockerels and compare for your self as you have the birds in front of you.
Does it crow at all yet? And can you see any sign of spurs on it that aren't on the other? Another thing I would look at is the saddle feathers (feathers at the top of the tail) they would be more drapy like but from the pics they both look the same. I'm not sure how long it takes wyandottes to mature. I had the same problem with my russians. Some were distinctly different but none crow. I was suppose to have 2 roos and 8 hens but its looking more like 4 roos and 6 hens. I identified them with the saddle feathers like some one on here said to try and its held up, the 4 'roos' are Much bigger than the 3 'hens' and have much longer drapy-er saddle feathers.
If the comb were wider id say roo for certain, but from most of the pics I've been looking at it does look like a hen, but maybe a little more mature hen. Are you certain they are the same age? Another factor could be they are from different parent birds, then one may have genetics to develop comb and wattles sooner/later than another. After looking more closely at the hens Id put my money on hen. And 17 weeks seams old enough to develop the saddle feathers, considering russians mature slow and mine are 3 months and have the definite saddle feathers and red-er combs and combs appear slightly wider (russians have miniscule combs even on roos) that would lead me to think it was a hen after looking up on your breed again.
Here's a small pic of some of that breed.
http://www.cheshirepoultry.co.uk/images/bluewyandotte1.jpg
I wish I could say for 100% sure, but I just don't know enough about wyandottes. Hopefully some of the info above will help you.
I hope a wyandotte expert sees your post and can say for certain. But for me from the pics and what I've seen I'd say shes a she.
Sorry for not replying in a more timely manner, my internet connection is very very pour and goes down often. I'll try and post pics if my internet will start working properly again!
