I would guess that everything being equal you would get a little more speed from the CG because it has more RD and thinner limbs but it would not be a lot. Probably not discernable to the naked eye and certainly not to the deer being hit with the arrow. As far as craftsmanship you are looking at two of the very best in the business and will get perfection from both bowyers so that is a wash as well. Then you take regional loyalty and discover both are Michigan natives and that goes out the window. Price point could be a bit different with the GN probably 100 or so higher but for a lifetime investment in a hunting bow that is usually not enough to sway one way or the other. So, it comes down to speaking with the bowyers and getting a feel for who you want to work with, turn around time and just gut feel. I have both GN and NM bows and shot deer with both this year so to save all the trouble I think you should order both - Point is they are both great, great bows and great, great people so you may need to flip a coin.
You will be happy either way.
Bob Urban