I am looking to upgrade my 70-300 kit lens and wondered if anyone has done a practical comparison between the new technology 70-300L lens compared with the old technology push / pull 100-400L mainly from an IQ and useability point of view.

I have done all the physical diameter, length, weight and cost comparisons but wanted peoples real life views on how they actually compare from a picture quality and useability point of view.

I also know that the 70-300L will not work with Canon 1.4x or 2.0x extenders and is very slow if used with other brands, the 100-400L can be used with the extenders but only in manual mode.

Decissions, decissions decissions.