Tamron 28-75mm for the 70d

I'm about to pick up the 70d tomorrow:

Still undecided on which lens I should get.

sigma 17-70mm (non contemporary)
or
tamron 28-75mm

how would the tamron work with the 70d's AF system? better than the sigma?

any idea guys?

No. The Sigma has an HSM motor, the Tamron does not.

The Tamron is a great length for portraits on a crop sensor but is not particularly wide for general use. It is not a blazing fast focusing lens and can hunt in poor light. In good light it is snappy, but it is not an ultrasonic motor and is not as fast.

I loved my Tamron 28-75, my primary lens on a 5d2 then 5d3 for a couple of years.

That said? I definitely felt left wanting with the AF, and the AF is also LOUD. So I'm quite certain if you used any of the phase detect AF while doing video on the 70d it would be one of the really disturbing sounding lenses.

I don't know anything about the sigma, just wanted to share what I felt about that Tamron, even though I was very happy with the pictures, and AF precision, the speed and noise left a lot to be desired and is ultimately why I broke the bank to replace that lens.