For landscapes, you'll be stopping down anyway, right? So f/2.8 doesn't buy you much. I would go with the f/4 (in fact, I did, and am happy with it). Image quality of the f/4 is very similar to the f/2.8


Wide lenses can be good for hand-held indoor photography because you can get away with low shutter speed, so they work well in low light. If that is what you want to do, you might consider the f/2.8 (or an IS lens such as the 28-105 f/4, which IRCC costs about the same as the 16-35).