I would like to buy one of these lenses.

Sigma 300mm F-2.8

Sigma 300mm F-4.0

Canon EF 400mm F-5,6

Canon EF 300mm F-2.8

Canon EF 300mm F-4.0

Can somebody give me feeback what the best is? Is there a big difference between Sigma and Canon?

Thanks in advance and best wishes for 2005