Which to buy Canon 100-400mm or Sigma 120-400mm
 

I can't decide between the Canon EF 100-400mm f/4.5-5.6L IS USM and the Sigma 120-400mm f/4.5-5.6 DG OS HSM APO, It is $500 different in price, but is it worth it ?

I will be using it for sport photography and video( shooting from the top)using 5D MKII / MKIII.
I read that the auto focus is not that great on the Sigma 120-400mm.
I am sure if I like the push and pull zoom action on the Canon 100-400mm.
As far as sharpness I' am not sure which one is better or they are equal.

Re: Which to buy Canon 100-400mm or Sigma 120-400mm
 

Rent both and try 'em.

Cheers.