Both use Canon CMOS chips with a native resolution of 1920 x 1080. Canon previously announced they would be 1/3" chips.
The camera features are similar, but the XF305 model adds HD-SDI output, genlock, and SMPTE time code (in/out) terminals for multi-camera or 3-D productions.
The cameras are scheduled to be available in late June for an estimated retail price of $7,999 for the XF305 and $6,799 for the XF300.
Ouch! I'd really been hoping [you mean dreaming-Ed] that the list price would be in the $4-$5K range to compete with the Sony NXCAM HXR-NX5U. But at this price point these will be compared with Sony's EX1 and EX3. The XF300 camera competes with the EX1 in price, but the EX1 has 1/2" imagers, while the Canon's have 1/3". The EX3 is a little more expensive than the XF305, but has an interchangeable lens mount.
The cheaper Compact Flash cards is a big plus over the EX series. One distinction with the previous Canon models was that they used CCD chips; and that's no longer the case.
But, what about that 4:2:2? That's what will get most people's attention. I'm really interested to see how the picture quality pans out. I'll be waiting to see the reviews. Unfortunately, at that price, I don't see myself getting one of these cameras, no matter how good the image quality.