D7000 paired with Sigma 17-50 f/2.8 OR.....

[rrwilliams64]

Would the Nikon18-70mm f/3.5-4.5G IF-ED DX suitably take advantage of the D7000 sensor capabilities?

or would the D7000 be better matched with , e.g., a Sigma 17-50 F/2.8 HSM OS. I have the 18-70, good copy w/ excellent IQ and minimal vignetting

...I also have the 50 1.8 and the 85 1.8; I recently came into a great deal for the D7000 which included the Sigma. (of course, I can/will take some pictures and compare the images from both glass, but simply looking for some input. I'd like to fully take advantage of the D7000 and thats where the decision between the 2 lenses arises) Note- The Sigma is new from B&H (invoice included dated 5/11), any copy issues can be addressed ... and the reviews seem optimistic.

But notwithstanding my 18-70, SB 400 and 50 1.8, would the 17-50 with fixed 2.8 be a no brainer? (I'd probably keep the 50 anyway, for $100 its always welcome in my bag.)

Thoughts?