Are you looking to apply as a Quebec skilled worker? You can see processing times here:
http://www.cic.gc.ca/english/information/times/international/02b-skilled-que.asp As you see, it's faster if you apply from the US.
It doesn't matter if you are a US citizen or not but if you are at a point that you can apply for US citizenship, you might want to consider it. You will lose your US green card if you stay in Canada too long.