I cannot say for the others but my Tokina 11-16 on a 1.5 crop sensor gives a FOV equiv. to 16.5-24 mm FF. It takes some mental adjustment to realize how to use the UWA aspect , Objects near the edges are distorted horizontally. The lens greatly extends the apparent distance between near and far objects, has a great depth of acceptably sharp focus. It is not usable for portrait work due to the way near objects (IE noses) are exaggerated. Also not really usable for horizontally panoramic vistas of distant mountain ranges whose peaks become mere pimples on the almost flat horizon. It's great dOF makes landscapes really sing when a near object (rock, tree , wildflower etc. is included to anchor the shot and provide a near object to enhance the layering of depth of the scene.
Also usable when physical constraints (IE a wall) prevent the camera from being far enough from the subject (IE family grouping) to get it all in the frame.

All stuff you probably already know though.
Great for long exposure night star shots (IE milky way) since it's DOF makes focus more forgiving and it's short focal length means the stars will move less during a long exposure thus enabling longer exposure time without star blur due to platform motion (earth 's rotation)

I cannot say for the others but my Tokina 11-16 on a 1.5 crop sensor gives a FOV equiv. to 16.5-24 mm FF. It takes some mental adjustment to realize how to use the UWA aspect , Objects near the edges are distorted horizontally. The lens greatly extends the apparent distance between near and far objects, has a great depth of acceptably sharp focus. It is not usable for portrait work due to the way near objects (IE noses) are exaggerated. Also not really usable for horizontally panoramic vistas of distant mountain ranges whose peaks become mere pimples on the almost flat horizon. It's great dOF makes landscapes really sing when a near object (rock, tree , wildflower etc. is included to anchor the shot and provide a near object to enhance the layering of depth of the scene.
Also usable when physical constraints (IE a wall) prevent the camera from being far enough from the subject (IE family grouping) to get it all in the frame.

All stuff you probably already know though.
Great for long exposure night star shots (IE milky way) since it's DOF makes focus more forgiving and it's short focal length means the stars will move less during a long exposure thus enabling longer exposure time without star blur due to earth 's rotation

You seem to be obsessed with sharpness, perhaps I am wrong. Sharpness depends more on you than on the lens. I have never used a lens that failed to give me the results I wanted.
Modern lenses are technologically speaking pieces of art. All of the new technologies are available to ALL lens manufacturers be it Ernst Leitz, Tokina or anyone else. It could be very difficult to find a lens that will not do its job when we do ours. I respectfully advise you to make a selection based on your needs and rest assure the lens will do its job. I use a Nikon 12-24 f4 AFS with my DX and FX bodies and it has all the wide angle focal lengths I need but that is me.
I am sure you know these lenses expand the background so it is very important to come close to your subject. I am sure you know that distortions are high with wide angles and that flare is common. Objects at the corners of your viewfinder will be distorted while the center rendering will be fine. Some of these extreme wide angles do not allow the use of a filter. Using a polarizer for landscapes with one of these is not advisable because the polarization effect is not even.
Do I need to say more?