Neither, and I'd buy one lens at a time as well, not both together. There is too much overlap between 24-70 and 17-40 for my tastes. I have a 16-35 and 24-70 and the overlap just isn't great, it means in the uniqueness department only 16-23 is different from a focal length perspective, and that isn't so dramatic of a difference. It is still very useful to have the zoom functionality that goes well beyond that, if you are walking about with just one lens, 16-35 makes a pretty good walk-around lens in many situations, etc. etc. But for landscape shooting where you don't need this sort of convenience, likely you are carrying around a tri-pod and as well likely have time to set up your shot, fumble with changing lenses, etc. etc., I just don't see the point of having an overlap and if you are very serious about it you will likely end up frustrated with the additional distortion that comes from zoom lenses.
21mm vs. 24mm doesn't seem worth in practical terms doubling up on. I'd rent a 17mm TS-E and if you like it and just go with that for a decent while, then later decide if you want more primes/TS-E's or if you want to get a standard zoom to cover the rest. Rent to see what works best for you.
