The comments on here are confusing me. You clearly state that you want to try some landscape shots, perfect. Let's figure out a UWA for you. I don't think a 150-600 (or any other telephoto) would be beneficial to you since you said that you shoot with your 24-70 the majority of the time, and that you want to work on landscape. If you want to shoot telephoto landscape shots, you already have one of the best lenses Canon makes in the 70-200 IS II. So unless you feel focal length limited, a super telephoto would not help you.
The first choice would be the 10-22 Canon. Often considered one of the best EF-S lenses out there. You get a truly UWA lens, that will last you for years and provide fantastic IQ. Your next best choice would be the 16-35 F4. From everyones praises, might be on of the best recent canon lenses created. The only problem here its that while 16mm is much wider than 24 on a crop, it might not be wide enough for your intentions. Only you can decide that. You could always purchase a used 10-18 to see how wide you need, and then decide to keep it or sell it and buy something else.
The 17-40 is good, but the 16-35 blows it out of the water. Many people also say that the 10-22 on a crop is better IQ than the 17-40 on crop. I can't comment on that, but it would be something to look into. The Samyang 14mm F2.8 is a fantastic IQ lens, and SUPER wide on FF, decently wide on crop. However, it is a manual focus lens. But how else are you going to get 14mm F2.8 without spending thousands of dollars.
You have lots of possibilities, with a few very good choices. In your case I would go 10-22 or 16-35 F4. The 16-35 will be a build quality much closer to your current lenses, but it would be as wide. If 16mm is wide enough for you, pick the 16-35. If it isn't, buy the 10-22. Either way you can't go wrong in the IQ department.