За информацией к первоисточнику к Кэнон
http://www.canon.com/camera-museum/tech/report/200304/200304.html
Это у 10Д
Evolution of digital features
(1) Large CMOS sensor with 6.3 effective megapixels
As did the EOS D60, the EOS 10D employs a large CMOS sensor with about 6.3 effective megapixels (out of a total of 6.50 megapixels) and an effective sensor size of 22.7 x 15.1mm (Photo 2).
Although the size and pixel count of the EOS 10D’s CMOS sensor are the same as those of the EOS D60, the EOS 10D achieves a higher sensitivity and S/N ratio as well as further noise reduction during long exposure, thanks to a new even more precise manufacturing method, new advanced peripheral circuitry and an improved built-in amplifier.
The EOS 10D incorporates the primary color filter and the hybrid low-pass filter comprised of two quartz crystal plates and a phase plate combined with infrared cut dichroic mirror and infrared absorption glass.
http://www.canon.com/camera-museum/tech/report/200309/200309.html
Это у 300Д
Digital features
(1) Large CMOS sensor with 6.3 effective megapixels
The EOS Kiss Digital employs a large CMOS sensor with about 6.3 effective megapixels (out of a total of 6.50 megapixels) and an effective sensor size of 22.7 x 15.1mm (Photo 2). The size and pixel count of the EOS Kiss Digital's CMOS sensor are the same as those of the EOS 10D.
In terms of the sensor's basic performance such as high S/N ratio and noise reduction during long exposure, the EOS Kiss Digital also achieves the same level of performance as the EOS 10D except for the maximum ISO sensitivity (EOS Kiss Digital: 1600/EOS 10D: 3200).
Если коротко -
Сам сенсор пластинка размером 22.7 x 15.1mm одинаковая что у 300Д, что и у 10Д, а компоненты электронной обвязки разные как весь узел в сборе - разный, т.е. сенсор+эл. разводка. precise manufacturing method, new advanced peripheral circuitry and an improved built-in amplifier
