Get them both, try them extensively and possibly sell the one you might not like later for the price you have paid for it or more.
No brainer.
I did test them both (plus the 14-24G and the 24-70G) and then decided for the 1.4/24G. Why?
Because
-- geometry is nearly flawless so I get a great feel of what the picture will look like after processing,,, before shooting
-- at 1.4 I can separate a single person in a crowd
-- the lens features very smooth transitons from sharp to unsharp parts (what it means see below, this is taken @f=1.4!!!)
-- The 14-24 has no filter option (except for Lee filters) and no protection of the front lens against sea water and sand
-- The 24-70 is a superb high contrast lens but I do not like the rendering style at all
-- the 1.4/35G features much more geometrical distortion, so in nature it is good in cities only after geometrical correction