I believe Canon chose CMOS because it is cheaper to produce, not for reasons of quality.
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Canon's worst current performer at high ISO (400D), still has less than half the read noise at ISO 1600 than the best Sony CCD. Canon's best, the 1Dmk3, literally has only about 5.5% the read noise of the worst CCD (worst in read noise, that is; not in general), in the D2X.
At the low ISO end, Canon also has the lead, by 1/2 stop, typically, at ISO 100.
Now, CMOS is supposed to mean a higher quantum efficiency, but in practice, the Sony DSLR CCD sensors to date have not had very high QE. The P&S CCD sensors have higher QE and and lower read noise than the DSLR sensors. The only reason they give inferior images is because of sensor size.