So I'm thinking about getting the eos r and I only have app-c DSLR lenses so I know I'm going to need to get a lens with it so which would be better for a first lens the wide 15-35L is 2.8 or the 70-200L IS 2.8?
I don't think there is a right answer, though the traditionalists will favour the wider angle 15-35. I know that I miss the wider angle I had on some of my higher end point and shoots; as well I get a lot of use out of a 70-300 zoom, though neither is of the quality you will be getting. You might go out with what you have and see where you are happiest shooting landscape.
My choice would be the telephoto for flexibility. You can create a "wide-angle" shot by stitching multiple images shot with a longer lens and post-processing, but there's really no way to simulate getting closer with the wide one.
Really depends on what you shoot most. The 15-35 allows you to go very wide indeed, equivalent to about 10mm on APS-C. At the 35mm end, it's still on the wide end. The 70-200 is a workhorse, but totally different in purpose.
