I need a bit more reach for sports photography (local GAA club U-8 and U-10) and have been considering these lenses. I currently use a Canon 80-200mm f2.8 L.
I have the 120-300mm Sigma. Lovely lens. It’s as sharp as a knife as well. I used it last saturday with a 1.4x converter which gave me a 420mm f4. The images are slightly softer at 100% crop with the converter but that was to be expected.
You can have a look at some photo samples here All of these had the converter on as well.