The different would be much more significant and noticeable if Canon had applied all of the newer tech while holding MP's steady as Nikon has been doing.
Errr.. you are out of touch with the current state of affairs. Clearly, you have NOT noticed the Nikon D3100 is 14 MP and the D7000 is 16 MP. On the other hand, the 600D has the same pixel count as the 550D, 60D and 7D. So, Canon has been holding the pixel count steady while Nikon is increasing theirs... and soon Nikon/Sony will be going for 24 MP.
In case you think Nikon improved on the Sony sensor technology in their D90 and D5000 as compared to the D300, that is wrong also. There is definitive proof that all Nikon did was to introduce destructive (albeit sneaky) in-camera RAW NR. I have the link at home and can post it later. This is one of those things NOT captured by the limited DXOMark tests.
Most interestingly, the D300s (released after the D90 and D5000) does not have the same in-camera RAW NR. The postulate is the processor at that time cannot cope with the relatively high fps of the D300s (as compared to D90/D5000). It appears that sneaky destructive in-camera RAW NR is practised by everyone these days EXCEPT Canon who wants to continue their support for the small astro-photography crowd. Sony did the same with their RAW files at one point but seemed to have stopped the practice after the barrage of complaints.
Proof of in-camera RAW NR on D90:http://forums.dpreview.com/forums/read.asp?forum=1032&message=32401883
Not sure if the pics will load 'cos the poster, Gabor, has passed away.