I have seen reviews which state that the 24/1.4 will better all of the zooms from at least f/4 and wider. Not suprising. Distortion is of course better controlled with the prime than any of the zooms, but I agree that if you only shoot landscape photography then a zoom will be much more flexible and will probably give indistinguishable results when both are stopped down. Regarding lens flare, the 17-40 is more resistant than the 16-35. The 24/1.4L does have a huge front element, but it also has a hood designed exclusively for 24mm coverage.
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Stu.