Scene shot with Canon 20D from monopod in RAW+JPEG_Fine.

Lens -- Canon EF 100-400 IS f/4.5-5.6; IS in mode 1.

Shutter speed 500th of a second; AV mode.

ISO 400.

Focal length 400 mm.

White Balance on Auto.

Neither image has received any post processing, including sharpening. 

The RAW file was converted to JPEG using Adobe Bridge>Photoshop. All Auto Adjustments were turned off. White balance set to "As Shot." The difference in apparent color derives from the color temperature settings in the Adobe RAW converter. Either image could have been adjusted to appear as warm or cool as the other. I chose to leave things as they came from the camera.

Since the shot was taken in RAW+JPEG Large_Fine, both images were taken at the same instant. The RAW file is
completely unprocessed. The JPEG file underwent JPEG compression, but all other in-camera settings (sharpening,
saturation, etc.) were set to zero.

RAW Image (well, actually it's a jpeg from the RAW, since you wouldn't be able to view a RAW image on the internet!) showing entire scene, reduced in size for download purposes.

JPEG image (shot as JPEG, Large_Fine setting) showing entire scene, reduced in size for download purposes.

100% Crops of the two images. 

RAW first:

Now the JPEG at 100%:

A significant difference? You're the judge!
Want to see the originals? Feel free to download them -- warning -- they are pretty large files!

Download RAW Image (you'll need to open it in a program capable of viewing Canon CR2 RAW files).
Download the JPEG Image.

On Pixel-Peeping
(Or the tendency to scrutinize photos to death.)
Read It HERE.