If you decide on the 16-35, why not consider the f4 version... Normally you will be stopping down for landscapes anyway, it is cheaper and it is a nice sharp lens.. I have one and it is a fantastic lens..
Yeah, that was definitely a consideration too. I am just thinking along the lines of having something for the long run, even if I decide to switch to a new niche. Seem like the 24-70 II is a pretty popular lens here; awesome IQ and no vignette when zoomed in like the 24-105. The larger aperture will definitely help in lower light HH shots vs. an f/4.
Going to the camera store after work to give them a try. So many considerations.