I list in both currencies and don't really notice much of a difference in my categories.
But my reason for choosing one or the other is bulk.
If an item can ship LetterPost/Light Packet (less than 500 gr/ less than 2cm) it goes on dotCOM where I use Flat Rate and usually Free Shipping.
Larger items that have to use Parcel services go on dotCA, because once we add distance to the parameters for the service, Flat Rate is impossible for me.
The one thing I have noticed over the past few years*,is that I am getting more European orders than I used to. I think this may be because Canadian sellers don't use the Global Shipping Program and therefore customers who have been burnt by that (urinating dog/ urinating dog/ urinating dog -- to quote Sir Terry Pratchett) service find our postage costs more reasonable than our American cousins.
This however is anecdote, not data.
* I closed my listings in Summer 2014 and did not reopen them until Fall, because we moved from Ottawa to Victoria.