Forgot to say the main reason for the insulated flex duct is too avoid moisture condensing inside the duct and running into the fan or at the fan and rusting the insides as well as running into the ceiling edges.
Also assess your present use. Is it so loud that some people don't turn it on? That is a good reason to get a low sone rating (so people will use it). Around my house they are so loud that they are underused by everyone but me and the day I develop a death wish is the day I will stick my hand in the door and turn it on while my wife is in the bathroom assuming I can stand it long enough to get close to the door.
Then consider whether you want to wire the fan direct to the light switch. I hate those loud fans that come on with the lights but a quiet one may make a difference and if there are people in the house that still won't turn it on even if it is quiet, then direct wire them together.
Rock chalk jayhawks next year, Chenowith crashed, Earl will never meet his potential, and Roy's boys just go from hot to cold to quick to have any consistency. They don't run and rebound like they used to and if they get a lead, they can't hold it against a quality team.