Similar deliberation a couple of years ago, I plumped for the Sigma 8-16... if you gonna go wide, may as well go all the way! Its an annoying trait of UWA's is that once you get some, it's never really enough.
Probably not the wisest choice, it was twice the price of the rest, and rather wobbly at the very wide side... 'tis W--I--D--E though! Great for getting into confined spaces and not chopping things of the edge of the frame.
Out of the more conservative alternatives; the Siggy 10-20 though has to be top-choice for VFM. And probably the older f4.5 rather than later f3.5. If
second hand or you can find old-stock. Its reputedly a slightly better lens optically, and cheaper, and when you have such incredibly closest focus and deep DoF anyway from such short lens, the extra stop of aperture doesn't 'really' make that much odds, just a brighter view-finder. Tameron compares very closely in reviews, but seems a slightly more 'budget' offering.
Nikon 12-24, is good, but expensive. Tokina 12-24 is very good budget rival to the Nikon, and apparently very very well regarded for IQ for the money; B-U-T neither go that bit wider, and on a crop-sensor camera, when you get down to these short focal lengths, 1mm does make a big difference to the amount of wide you get. So Siggy 10-20, has to take the cherry on all round points.
But be warned..... Tele's serve up instant impact, cut clutter and concentrate viewers attention, very easily. Go wide? Everything gets compressed, and impact and drama diminish, and they all start to make you have to work an awful lot harder to get what you expect or hope for, and dodge both distortion and 'wired' perspective; Packing so much in the frame, the devil is in the detail, and there's often a LOT of it to have to look at, and its 'small' and distracting day-glo blobs of dog harnesses or crisp-packets and things you don't 'see' in the view-finder during composition, can leap out when you look at the image on a 17" monitor.