I would not recommend the Nikon lens for your needs. I am not going to criticise the Nikon image quality, which is superb, but that lens has real and severe downsides for a crop-frame landscaper to create images in the first place. In saying what follows, I am a full-frame shooter (5dII) who seriously considered the Nikon. I actually got to test one with the adapter and decided very quicky that it was not a good lens for my needs.
As a crop-frame shooter, the Nikon is not an ultra-wide zoom, but more a general wide zoom (22.5-38.5 equiv) with not a broad enough range to be a practical general lens. It is very bulky, very heavy, and has a very large front element that cannot be protected from the elements. If you damage the element, every nick will show in the image. The lens does not accept filters and there has been no third-party solution that is not ridiculous and the attempts so far have been unworkable. This is a huge downside for landscapers. No polarizers (they are still essential even with ultra-wides to remove glare from water, saturate colors on overcast or rainy days, accentuate rainbows, and, yes, even to partially darken of skies). No ND grad filters (these allow you to get, in five seconds, the exposure balance it would take an hour or more on the computer--if you could to it at all). No ND filters to slow exposures for "foggy" water or blurred cloud movement in skies or, if you shoot video, to control video exposures. No protective filters for harsh conditions (blowing rain, snow, sand, etc). The lack of exif (to evaluate and repeat experimental exposures), and stop-down metering are, in fact, significant disadvantages once you actually have to experience them. If you camera does not have live view, achieving critical focus is almost impossible at working apertures of f8 or f11 (focusing wide open and then stopping down for exposure is risky because the focus point can shift when stopping down).
If you do not intend to shoot full-frame, I would definitely not get the Nikon. Canon has a by-all-accounts excellent 10-22 EF-S lens for the crop format. This gives you a true ultra-wide 16-35 equivalent. The lens is a high-tech design with several aspheric and a UD element, with really solid construction. It would rate an "L" designation but for the crop format. It is light, compact, and fully filter compatible. It is not a constant 2.8, (3.3-4.5 I think?) but you are shooting small apertures and the size and bulk from the constant 2.8 is of only limited benefit to landscapers as you know. I think this would be a far better choice for your needs as you described them.
If you want for some reason to get a full-frame lens, all of the downsides of the Nikon still apply (except you get back the ultra-wide range). If you are not satisfied with the Canon 16-35 full frame solution (as I was not), then I would look for a Contax "N" / Carl Zeiss 17-35 2.8 that has been converted to use on a Canon. The converted lens operates exactly like a Canon with full autofocus, autoexposure wide open, and exif. I have been very pleased with this lens in terms of distortion control, overall sharpness, flare control, and color rendition. It is a very close second to the Nikon for quality, and is fully filter compatible with no exposed front element. A far better choice for landscapers for these reasons. The company that does the conversions is called Conurus. If you want to find an already converted lens, You will need to look on ebay, fredmiranda.com, photo.net, here, or getdpi to find one. They are rare but a couple do come up each year. Or, you can buy the original Contax N version (that is more common) and send it to Conurus for conversion, but you may have to wait many months to get it back. Their conversions are first rate but they are a small shop and so it takes time. You will end up spending more than the Nikon, but have a much more useful lens.
Otherwise, I would rent, borrow, or buy (with right of return) the EF-S lens and try it. Do the same with the Nikon but be careful about buying a Nikon as the adapter mounting process might modify the lens and void your warranty or right of return.
There is a clear difference in a lens' image quality versus its ability to allow the photographer to capture image variety, and my choice was for the latter. Slightly higher quality shots of a much more limited palette of subjects just did not appeal to me.