I am a nikon shooter (d200), and I am so happy with my equipment but when I watch photos taken with canon's 5d or markIII I am absolutely stunned.
I can't shot over iso400 and canon's shooters can shot iso3200 every time they want.
I went to a party the last weekend and there was a photographer with a markIII camera; He was shooting without flash when the people was dancing in the dark.
I asked him about the flash absence and he said to me that He had a free 5 stops more card.
That was amazing, He was shooting at iso3200 without problems!