I'm in Canada too, and end up getting my paper from a local print shop / art supply store. Only because I avoid the big chains if I can. It's the same stuff from both though.
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I tend to switch back and forth between card stock and thicker copy paper.
Lettermark Vellum Bristol 67lb / 147gsm (Ivory) is what I'm using now.
My Sweden collection is on Hammermill 28lb / 105gsm premium copy paper (white). And I use this paper for title pages, which tend to be more colourful. The colours pop against the white more than the cream card stock.
The perfect world for me is the 28lb / 105gsm light cream paper. But I can only seem to find it in white (too bright for my eyes) or a too-yellow tone of 'ivory'. Which is why I seem to switch back and forth.
I agree with barhata that the card stock is great for mounting booklets or covers. I find that a binder full of it can get pretty thick though.