100-400mm f/4.5-5.6 IS czy 70-200mm f2.8L IS + Canon Extender EF 2x

co lepsze:

100-400mm f/4.5-5.6 IS
czy
70-200mm f2.8L IS + Canon Extender EF 2x
?
:?:
:idea:

http://www.canon-board.info/search.php

http://www.canon-board.info/showthread.php?t=12771