Hanoi is quiet and more laid back then Saigon, but for the majority of people, no one really wants to be based in Hanoi but most people when they come here they tend to stay instead of requesting to go to SGN. However asking SGN folks to come to Hanoi is like drawing blood out of a stone!!
SGN is where all the fun is at!! Not too many better places in Asia for single (or married guys, if you get what I am saying......)