Budget-minded sports lens for Sony dslr?

Which is better for action sports? 1) buy a used Canon FD 300mm f/2.8 (or Nikon ED) & adapter for Sony 2) buy a used Minolta 300mm f/4.0 w/o adapter. Looks like 1) is a bit cheaper, but I'm not sure if the qaulity/focusing is still good with the adapter. FYI I have a new 70-200mm f/2.8.

The used Minolta.

The adapters you will need (if they exist) will eat some light, maybe a full stop.

Minolta made excellent lenses and the one stop difference can be adjusted by using a the sensor ISO to keep high shutter speeds to prevent blur

You already have the 70-200mm. Isn't that already enough? My concern with the adapter wouldn't be focusing. It will work manually even if it won't focus to infinity. A bigger problem is that you might lose the lightmeter then it would be up to you to set aperture and shutter manually but that might not be a problem to you at all. Still, between 300mm and 200mm, the difference is relatively small. You can crop your way out of it if needed.