I mostly shoot landscapes and this year I want to do this with my D3x (and not LF). So I'm looking at two of the sharpest wide-angle lens available from Nikon (I think)
If you intend to use a WA for landscapes, you should consider also the Zeiss ZF 21/2.8 over the 24/1.4.
The 24 PC has its own advantages, due to tilt and shift.
I guess you know that these features are very useful in landscape photography (to those who are not familiar, I suggest reading
http://www.cambridgeincolour.com/tutorials/tilt-shift-lenses2.htm and
http://www.cambridgeincolour.com/tutorials/tilt-shift-lenses1.htm ).
I have used both 24 PC-E and 85 PC to get 20+ Mpix files with my 12 Mpix DX camera (D300). I used shift and stitching in CS4.
This way I could obtain a file similar (in terms of pixel count) to a D3X file. However, I noted that the 24 PC-E has some tendency to show CA at the borders when shifted. Also border sharpness decreases when shifted (note that my experience was on DX). The 85 PC performs better, probably due to its easier/simpler design.
In conclusion, if you need Tilt & Shift capabilities, and/or you wish to use stitching in a simple way, the 24 PC-E is the lens for you. If you need a world class WA for landscapes, then the Zeiss ZF/ZF.2 21/2.8 represents the best WA ever produced for 24x36 SLRs (digital or not). It's cheaper than AFS 24/1.4 (see
https://photo-shop.zeiss.com/epages/cz.sf/en_GB/?ViewObjectID=5719321&Locale=en_GB ).
Finally, if you need a fast WA, well the 24/1.4 is the tool you have to use. At present time, I've not seen any clear indication about the 24/1.4 performance in landscape photography. Most of the files you can see in the web show reportage/street pictures.
Best,
Riccardo