I think a question is ask yourself is what range you shoot most in. I personally have a 17-50 (which translates to about 26-75mm), so it gives some wides, and into the normal range, and I shoot mostly in this. I have a 12-24mm, but do not use as often, and I'll pull it out for more specific uses. A 12-24, or 10-22 is hard to keep on the cam all the time. A 28-75 (which translates to about 42-115) lacks a bit on the wide range, so this lens becomes more of a "portrait" lens. I owned a 35-70 lens, which was great as a portrait lens, but lacked the wide end, so I had to keep changing lenses. So which lens would you take if you have to take only one out?