Bryan has posted the image quality shots on TDP. Where it overlaps with the 100-400mm II, the Canon wins up to 400mm, usually with a wider aperture as well, eg
http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=978&Camera=453&Sample=0&FLI=4&API=0&LensComp=972&CameraComp=453&SampleComp=0&FLIComp=3&APIComp=1\\
The 100-400mm II + 1.4xTC at 560 mm is very similar to the 150-600mm at 600mm. The difference in weight is colossal, the difference in operational weights is 2.65 lb (1.2 kg) with the extender attached to the Canon or 3.2 lb (1.46 kg) without.
http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=978&Camera=453&Sample=0&FLI=4&API=0&LensComp=972&CameraComp=453&SampleComp=0&FLIComp=3&APIComp=1\\
The 100-400mm II + 1.4xTC at 560 mm is very similar to the 150-600mm at 600mm. The difference in weight is colossal, the difference in operational weights is 2.65 lb (1.2 kg) with the extender attached to the Canon or 3.2 lb (1.46 kg) without.