Serpent said:
US prices are much better. Some good stores:
www.nordstrom.com
www.saksfifthavenue.com
www.neimanmarcus.com
www.macys.com
Brands: Hugo Boss, Faconnable, Andrew Marc, Armani
Comparable Canadian stores are Harry Rosen and Holt Renfrew.
Being an American - I'll second Serpent's post. Closest nice American mall to Toronto would be Galleria.
http://www.waldengalleria.com/
Coach has very nice leather products - a bit pricey, but quality is there.
If you want to leverage your at par Canadian dollar - try going to the outlet center on Military in Niagara Falls, New York. Very nice designer items at a deep discounts.
http://www.fashionoutletsniagara.com/
Be cognizant of the maximum amount of purchased items you are allowed to bring in to avoid tax. It's been a while, but I recall as an American you are allotted about $400 of purchased items outside of the US for the day without being charged tax. I don't know what it is for Canadian citizens purchasing American goods so check.
Bring those valuable Canadian dollars right here to Buffalo! (People used to say for us Americans to bring our greenbacks to their Country - now it's the other way around
)