Sigma 300mm F2.8 with TC, or Sigma 50-500mm F4-6.3?

I'm shooting sports, nature and surfing. I need a longer lense, but I cannot afford a 500m F4. So which of

these two is better? Does the 300mm do well with teleconverters? I know the 500mm below is slow.

 

1. Sigma APO 300mm F2.8 EX DG/HSM with 1.4 and 2x teleconverter, or

2. Sigma APO 50-500mm F4-6.3 EX DG HSM

 

Any comments are appreciated.

The 1.4 works well with the 120-300 so it should be fine.

Thanks Mark. To clarify, I would also like comments on using the 2x TC with the 300mm

F2.8. I need 500-600mm for some shots, since 420mm doesn't bring me close enough.

I would go with the 300 f/2.8. Sigmas super zooms tend to not focus very fast. Anything with a 2X converter will be slower to focus, but I shoot with a Canon 300 f/2.8 and love it. A prime lens I think is just sharper than a zoom. It gives me more versatility to crop the way I want. If I need to get closer, I throw on the 1.4X teleconverter. You'll need that f/2.8 on cloudy days or at night games.

I owned the 300 f/2.8, and 1.4tc. Great combo, fast focus. I used a 2x on it a few times, and

the results were quite acceptable, but not as sharp as the 1.4 which is to be expected.