Nikon buy in the best sensors they can from Sony and elsewhere, while Canon make their own; of course that means that all the while third party sensors are better, Nikons can outperform Canon.
BUT...because they're using third party sensors, Nikon never get to pull ahead of the other brands particularly who also use the same modules (eg Pentax and Sony), and their superiority over Canon only works for as long as Canon's sensors are behind the curve. The advantage Canon have is that if they pull out of their current trough and start producing sensors which are better than the competition (as they were doing for some time before this), then they alone will profit from that - their cameras will outperform EVERYTHING else again, which has to be the stronger position to be in.
BUT...because they're using third party sensors, Nikon never get to pull ahead of the other brands particularly who also use the same modules (eg Pentax and Sony), and their superiority over Canon only works for as long as Canon's sensors are behind the curve. The advantage Canon have is that if they pull out of their current trough and start producing sensors which are better than the competition (as they were doing for some time before this), then they alone will profit from that - their cameras will outperform EVERYTHING else again, which has to be the stronger position to be in.

