24-70 F2.8 vrs 17-55 F 2.8 for G.N photography

[albion14]

HI.

Looking at either a Canon 24-70 f 2.8 or a 17-55 F 2.8 IS for a crop sensor camera,for use in G.N. I know there are many users of 40D's and 450 D's that use some sort of the above combonation.

let me Know your views on the above lenses.In this country both lenes are almost the same price.I like the quality build of the 24-70 but like the reviews of optics un the 17-55,and it has I.S,but the build quality I am told is poor-dust issues,plastic body.

So which of the above should I buy for a crop sensor to be used for G.N?

Thanks for any pointers A14