Yeah the American HD's have a much wider selection of lighting products. Last time I was there I got some choke ballasts which were impossible to find in Canada.
I believe Lowe's and some Rona stores sell a wider selection of HIDs though.
Lowe's has 100, 175, 80, 400 watt MV, 70, 150 watt HPS, 70, 175, 250, and 400 watt MH at my local store. I bought a MV 175w yardblaster at Rona, they also had a 150w, 70w yardblasters (HPS),wallpacks (HPS), and 150w HPS bulbs.
I believe Lowe's and some Rona stores sell a wider selection of HIDs though.