I take photos during rugby matches ( floodlights) and soccer ( my son always in daylight). I use the 1D MKIII and Sigma 100-300/4. Recently the lens is 'soft' at 300 and very good/excellent up to 250mm. I also have the 1.4x and use it only during daytime rugby games but slows the AF and the IQ is good to average.

I am thinking to buy either the 300/4 or 400/5.6 ( Santas's present to me). The 400 is great for reach but the 5.6 will not be ideal for evening matches although the 1D MKIII produces acceptable noise at ISO 2000 - 2500.

The 300/4 will be great for evening games but not long enough.

I will probably send the Sigma to be checked and keep it because i like the flexibility of the zoom when the action happens close by.

Which one would you go for the 300/4 or 400/5.6? Can't afford the 2.8s

Thanks
John