For what it's worth, a few months ago I finally completed my own personal evaluation of several wide angles for use on my D800E. Evaluated were the 14-24/2.8, 24/1.4G, 35/1.4G, 28/1.8G Nikons, at the time I personally owned these, and I had some short term evaluation experience with the Sigma 35/1.4, Zeiss 21/2.8, Zeiss 28/2 and Zeiss 35/2 lenses. To cut to the chase, after that period of evaluation, my current wide angles are:
The 14-24/2.8G: Used for focal lengths between 14-18mm. At 21mm the Zeiss 21/2.8 is strong competition, although some scenes might be better rendered by the Nikon (I'm thinking scenes with a lot of water and cool tones). Overall though, after shooting both, I'd say the Zeiss 21 is my preferred lens at this focal length. I will say this: the 14-24, as good as it is, is a VERY cool rendering lens that has a distinctly whitish coloration to the highlights that the Zeiss 21 and other top level Nikons do not have. At 24mm, there are slightly better options, namely the 24/1.4G. The 14-24 is definitely a legendary lens, but on a D800E, it is not as perfect as perhaps some make it out to be. At the end of the day I think of it more as a set of ultra wide primes (14/15/18) than anything else. I'd rank it as "very good" at 24mm whereas I'd rank the 24/1.4G as "excellent" if that helps.
The Zeiss 21/2.8: No, it's not perfect; it has some cyan color shading in the corners, some distortion, and in some situations the forward corners of the 14-24 might "win". However, simply put, the Zeiss 21/2.8 has magic. It is one of my very favorite wide angles lenses, without question. The more shoot with this lens, the more I don't shoot with my other wides, which is really all there is to that. While not quite as flare resistant as, say, the 24/1.4G or 28/1.4G, I do feel the T* coating is about the best there is in terms of color neutrality and consistency from shadows to highlights, and the thing is just sharp as bloody hell with real life subjects. It does seem to be biased somewhat to really excel with compositions that have a predominant central subject; it's in these compositions that the famous Zeiss "3D" look is obvious. Strongly, strongly, strongly recommended for D800E shooters.
The Nikon 24/1.4G: Again, not perfect (no wide angle is.) Takes F/6.3 - F/7.1 to get corner and edge sharpness where you'd like, but this lens has everything that I find positive about the modern Nikon "G" nano-coated lenses: tremendous contrast, strong, pure colors, nice OOF rendition, and a strong, bold rendering with a lot of clarity. This and the Zeiss 21/2.8 are my favorite wide angles on a D800E. I feel it is better than the 14-24 at 24mm, particularly for distant subjects. (The 14-24 seems to shine more at closer range subjects on the D800E at 24mm while the 24/1.4G is fairly even in terms of performance across all distances)
The Nikon 28/1.8G: This one was a surprise. Derided by many for its strong (and it is strong) field curvature, I have found that if one is willing to experiment and understand its tendencies (field curvature and some focus shift), it is capable of astoundingly good results. Its microcontrast gets closer to the Zeiss ideal than any other Nikon wide, it's professionally sharp, and has excellent contrast. It also is about as flare resistant a wide angle as I've ever found - surpassing (easily) the Zeiss 28/2 or Sigma 35/1.4 in this regard. Head to head tests with the Zeiss 28/2 left me preferring the Nikon, mostly for better edge performance at distance. A lens I did not expect to like, that I do, although I am aware of its many, many quirks. I didn't expect to be a buyer of this lens, yet after time spent with it, I was. I will note it is built like crap. Absolute amateur plastic crap. However, when it is in "the zone" and the field curvature figured out and such, one can see hints of absolute brilliance. It makes me wonder what would have happened if Nikon had NOT put a budget/price constraint upon the designer - if this lens had been made in Japan under more typical high end Nikon standards and been designed without as much field curvature, this could have been something mind blowing. As it stands, it still is quite good, but perhaps a lens that must be "learned" to get around the quirks of performance.
The Sigma 35/1.4: Sharp sharp and sharp. Most importantly, unlike the Nikon 35/1.4G, it is professionally sharp at landscape apertures and landscape distances at the edges on the D800E, something the 35/1.4G just didn't quite achieve. Rendering is quite different from the Nikon G lenses, more "clean and crisp" as opposed to "bold and strong". It's not perfect - overall contrast is not quite as good as the best Nikon or Zeiss designs and flare resistance is good but nowhere like the best lenses, but it's stupid sharp, and that's what I need a 35mm landscape lens to be. I preferred the Sigma over the Zeiss 35/2 and Nikon 35/1.4G, the latter which was soon sold.