I personally prefer the longer but lighter 70-300 IS to the shorter but heavier 70-300 DO IS. If you shoot RAW and don’t mind a little postprocessing to up the contrast, you’ll be very happy with DO pictures. If you want to shoot jpgs and don’t want to sweat the images in Photoshop, you’ll probably prefer the standard 70-300 IS.

The 70-300mm f/4-5.6 IS L lens, however, puts the other two to shame, not only optically, but in feel and overall performance as well. The image stabilizer is improved, the lens is weather sealed to help keep out unwanted dust and moisture (though a front filter is required to make the lens truly weather resistant), and given the “L” branding means it has the best optics and build quality you will find in a Canon telephoto zoom. The only downside (other than cost) is that the 70-300 L is almost a pound heavier than the other two lenses, so keep that in mind.
April, 2013