I haven't used either lens, but it sounds like a good plan to me.
Honestly I don't understand why Bryan says that he recommends the 17-40
to crop users in his review of the lens. Why would you take a lens that has been engineered specifically for ultra wide angle performance and crop it? The ISO charts show even the 17-85, with its much larger range and IS as performing only slightly worse, and the 17-55 does better at 2.8 sometimes and easily better at F4.


You are right about the build quality and weather sealing, but I'm not sure about holding resale value better. I hardly ever see 17-55s come up compared to the many 17-40s on my local CL and they never sell cheap. Unless you are in some very treacherous conditions why would build quality ever trump IQ? Don't fall into the trap of being more concerned with your photo gear than your photos


Sorry to rant on the 17-40 as a general purpose zoom on crop, but it's been bothering me lately Maybe just cause I'd rather see it on my 5D :P