I just installed a WhisperGreen 80cfm fan (without motion sensor) in a 10' x 6' sloped-ceiling bathroom. (FV-08VKS2) I got it for 126 bucks + 25 shipping online.
It uses 3 elbows in its 4" ducting plus about 2 feet of straight pipe, angled down slightly towards vent hood in the gable wall. Everything smooth aluminum with insulating jacket. Taped with foil tape, not screwed.
Broan ecoVent (EV-100) vent hood (the one with the styrofoam ball valve rather than a flapper door) so no banging noises on windy nights. In hindsight, this hood is *not* a good match for Panasonic pressure-sensing fans due to resonance of the styrofoam ball. I'll explain further in a separate post if asked.
The one very noticable feature about this fan is that it is almost silent (eerily so) when it has no downstream loading. Once the ducting is connected to the vent hood (the largest resistance in the whole setup), the fan speed automatically ramps up to about 3x the original motor speed to attain the rated 80cfm.
The resultant sound is all white wind noise (though still very quiet) with no discernable motor noise.
Because this particular fan will increase its speed to guarantee 80cfm, I'd recommend going with it rather than the 130cfm model. You'll get less backflow resistance (and less likelihood of condensation pooling) if you use smooth metal ducting.
Instead of using the motion-sense model with a turn-off switch, consider using the non-motion-detector fan model with a humidistat--that'll keep the fan on high-speed long enough to guarantee a condensation-free bathroom rather than having to guess how many minutes delay your motion-detector should be set for.
The wall switch is meant to handle the case where you want to be able to force the fan off, say, if you have the Idle Air Volume switch set to a non-zero value. If you set the Air Volume switch to zero, then theoretically you won't need a wall switch. Not sure about Cdn code requirments though.
Does this help?