Sigma 17-70mm f/2.8-4,5 is a very good lens, I have mine in Sigma's SA mount with AF motor.
Too bad the aperture is 3,2 at 24mm and 4,0 at 35mm. It would be great if the aperture was 2,8 up too 35mm. Something between 24-35 in focal lenght are great for indoor shooting and I usually need 2.8 if I don't have flash.
DA 17-70mm f/4 is also a great lens. Pretty fast and silent AF. It was this or the Tamron 17-50mm f/2.8 for me. The focal lenght is perfect, it's wide and long. You don't have to change lenses all the time. All my lenses overlap, 12-24, 17-70 and 50-135, it's just practical
I recommend both of them, Sigma 17-70mm if you don't need the SDM(or don't have the ca$h).
I have owned DA 16-45mm f/4, didn't like it. Too short and I hated that it was extended at 16mm and normal at 45mm. It is cheap and good for it's price. And there is the CA problem.