Which Telephoto Zoom should I buy?

Sigma 125-400 F4.5-5.6 OR Canon 70-200mm F4L

I shoot sports (equestrian) so thats why Im intrested in the F4L
I want to start shooting Wildlife and thats what interests me in the Sigma
Is either one of these lenses good for both?
I rarely shoot in low light and indoors, so I don't think I need anything better than an f/4.

For equestrian I'd go for the 70-200, I use the Sigma 70-200 f/2.8 for about 95% of all my equestrian event shooting, the f/2.8 does come in handy sometimes if the light is cr*p

The Sigma is going to be of more use for wildlife i'd say.