Which UWA lens (for Nikon) is best for landscapes?

I have a Nikon D90 and the main type of pictures I shoot are landscapes. I have the kit lens (18-105) and am going to buy a 35mm prime because I miss the 50mm I had on my FE film camera back in high school. Anyways, along with that 35mm prime I wanted to get a wide angle to help me capture wide expanses. The lenses I was considering are:

(In no particular order)

1. Tokina 11-16mm f/2.8
2. Sigma 8-16mm
3. Sigma 10-20mm (f/4.5-5.6)
4. Nikon 10-24mm

Which is sharpest, best quality, and most worth the money? Which will probably be best for landscapes and travel?

In order:

Nikkor 10-24 mm
Tokina 11-16 mm f/2.8

That is it.

Here is what a Nikkor 12-24 mm does when attached to an old D100, 6 mp sensored camera

I've used the Nikon 10-24 and wasn't impressed. I do like the 12-24, though.

The Tokina is the sharpest and the 8-16 is obviously the widest BUT has pretty crazy distortion (which can be corrected for in post).

THe 11-16 is also very well built (and, obviously, the fastest).

http://www.dpreview.com/...-5p6_n15/4

If you don't have a sturdy tripod, get one.

If you want supersuper wide, get the 8-16. Otherwise, get the Tokina.

All of these have their strong points.

1. Tokina 11-16mm f/2.8
The fastest and therefore most suitable for handheld indoor architecture shots (low light conditions). Brilliant corner sharpness, but quite some chromatic aberrations (can be corrected in lightroom, but you have to find a lens profile on your own). I use this one myself and love it.
Also works on full frame/film at 15-16mm

2. Sigma 8-16mm
The widest, obviously, and therefore possibly the most suitable for extreme landscape shots. Good reviews. Can't mount filters, in case that you want to do long time exposures with e.g. Extreme and filters.

3. Sigma 10-20mm (f/4.5-5.6)
Convenient zoom range and affordable, a good compromise. Good reputation regarding the image quality, but it's slow.

4. Nikon 10-24mm
Biggest zoom range but also the most expensive. Image quality is reported to be good, but i can't tell much about it.

I haven't used them all so can't tell you which is the sharpest.

I have the Sigma 10-20mm F/4-5.6. Yes it is slow but the image quality and zoom range are fantastic. Build quality is very good. Unlike many lenses the hood is included as well as a very useful case. The price is pretty good too making excellent value for money. I love it!