Canon 600D wants to start with a wide-angle lens of Canon and ask for advice.

EF 17-40mm f/4L USM is good! EF 16-35mm f/2.8L II USM is a professional lens, which is very good! The price is also expensive! But when they are installed on your camera with aps-c size sensor, they can't play an advantage, because your sensor area is small, and you can only use the central part of their lens. However, their advantage lies in the quality of edge imaging, so it is basically a waste and not worth it if you buy it! In addition, the three lenses you mentioned are similar in central imaging quality, so 18- 135 with 600d is the best choice, with high cost performance!