Canon 100-400IS -vs- 70-200 2.8IS w/2x teleconverter ?

Can you please give me some advice ?

I already have Canon 70-200mm f2.8 IS and Canon 2x teleconverter. My camera is 5D.

I'll be shooting some hockeymatches the next weeks. The combination above is "more or less ok" (- actually not ...).

But how much better is Canon 100-400mm f4.5-5.6 IS at 3-400mm than the converteroption mentioned above ?

And prime Canon 300mm f4 IS ? From the first match I shot, it seems that quite a few shots were taken around 300mm. How much better optically is this lens compared to the 2 options mentioned above ?

Thank you very much !

(Pictures from the first match is here: www.pbase.com/hildrup/​friskasker)

In my oppinion, the 300 f/4L IS would be the best lens for your case. Throw on a 1.4x tele and you've got a winning combination.

The 100-400L IS would be second best, of course it will offer a little more versitility.