Canon 300mm zoom lens - what to get?

Hi All,

I am currently shooting with a 24-105mm USM L lense whihc I am mostly using for travelling. Lately, I have been attending some motorsport events and also become intereted in shooting a bit of wildlife. In that connection, I am considering getting either a 200mm or 300mm zoom lense.

I am not 100% sure if I should go for a 200 or a 300, but my first asumption would be a 300 based on trying some of the equipment of fellow photographers.

Looking at 300 lenses, I can see there are different options. First, I was considering the EF 28-300mm f/3.5-5.6 L IS USM lens, but I have read in a review that it is not very fast, which is a bit of a concern. As an alternative I am considering the EF70-300mm f/4-5.6L IS USM, however, as I have not been able to compare the two, I am not sure where to go from here. I therefore hope for some advise.

What I would be looking at is:

- Canon EF L lens, USM

- Zoom lens up to 300mm

- Fast

Hope some of you are able to share a bit of knowledge so I can go out and buy a lens which get closest to what I need.

Thank you