Bias Binding vs. Facing

Just a very quick question that I need some help with. 

I’m making a dress for my Mother In Law who visited the other day for a fitting.  The dress is Simplicity 5961 and we are making View 3 so no embellishments and it is being made out of vintage dupioni ruby silk.  She came for a fitting last week and I’ve made a number of adjustments that I will blog about soon, I was talking to friends mum who has years of experience about the dress and she recommended instead of hemming the dress I used bias binding as it would be cleaner and less bulky, I’m completely on board with that and I’ve adjust the hem length to take that into consideration.  I’ve made a slight adjustment to the bodice neckline as there was a bit of gaping on the muslin/toile so I pinned it into a dart.  I wasn’t sure how to reflect that change onto the paper pattern but my friends mum suggested just shifting the pattern off the edge of the fabric fold to make that adjustment.  I’ve tried it in principle and I feel that's correct but does anyone have a different view? 

Also because there is this tiny adjustment to the neckline it means I’ll have to do the same with the facing but it got me thinking (whilst in Zumba class of all places!) couldn’t I just use bias binding on the neckline as well?  I’m not a huge fan of facings as I feel they cry out home-made whereas a bias binding neckline a la Pendrell seems more of a  RTW technique.  Is there any reason to use a facing over a bias binding finish?

Also can I get bias binding specifically for silk or will regular cotton binding from the haberdashers be ok?  I don’t think I want self fabric BB as that would result in more bulk. 

Thanks for your help and I promise to reward you with a more interesting post soon with pictures of my muslin/toile and the fitting!