Hi,

Yes, as mentioned by ahab1372 and from my personal experience, you should find 24 really not wide enough on your APC. I have the 17-55 and I think it's an excellent lens I wish I could take with me the day I go for a full-frame. I've never tried the 15-85 which has obviously a bigger range but the constant f/2.8 + IS combo of the 17-55 does wonder indoor.