I would lean toward the lens that fits the body you're going to be using. 17-55 for the crop, 24-70 for the full frame.


I also keep the crop body mostly for telephoto and macro (and only some macro), as well as high frame rate requirements.


FF will let you get the most out of an EF lens. If you're doing standard field of view or wide, an EF-S series is simply more cost-effective for a given amount of performance. With an EF lens on a crop body, you're tossing more than half of the image away before it even gets to the sensor.