Canon commissioned Alan Roberts - who has conducted tests for the BBC on other cameras - to evaluate the cameras, and he's produced a report that concludes:
This camera performs well at HD, for such a small image format. Resolution is very well maintained and is refreshingly alias-free. Detail controls work well, and the factory settings are good. Noise levels are typical for 1”/3 sensors, but sensitivity is unusually good. Operating the camera at significantly lower gain will reduce the noise level without sacrificing significant sensitivity.The report, in PDF format, can be found at Frank Glencairn's website. Glencairn also includes separate notes from Roberts which specifically talks about the difference between the performance of the 1/3" sensor Canon XF camera's to the Sony 1/2" EX cameras:
The integral lens has a maximum aperture of F/1.6, unusually large for a small camera, and there was no perceptible loss of resolution through iris diffraction until the lens was stopped down to F/8, at which point significant resolution was being lost. Again, this is unusual for such a small image size. Thus, the camera has a useful aperture range from F/1.6 to about F/6.8. This, together with the 3-stage neutral density filters (each providing a further 2-stops of control), means that the camera has a much better exposure control range than is normal in a small camera.
...the 305 appears to out-perform the EX in all respects, if only marginally, which is entirely the wrong way round, it shouldn’t be so,. Clearly Canon have been doing some very clever things behind the scenes for a while, some of which I still don’t understand.”
Frank Glencairn: Alan Roberts (BBC) tested the Canon XF300/305 – and behold, he saw that it was good
XDcam-User: Canon XF300 and XF305 get BBC approval
BBC: Commissioning: Producing in High-Definition
B&H: Canon XF300 [Note: it's currently in-stock at B&H]