There isn’t a clear universal winner based on the community input. With two very similar APS-C f/2.8 zooms, sharpness often changes by focal length, aperture, and even center vs. edge performance. Copy-to-copy variation can also be large enough to matter as much as the brand/model difference.

From the answers provided, the strongest firsthand report is that the Tamron 17-50mm VC is quite sharp, with one owner finding it comparable to a 50mm f/1.8 prime when both are used at f/2.8. It also improves stopped down, especially around f/4, which is typical.

So the best conclusion is: neither lens can be declared definitively sharper in all situations from the evidence given. If sharpness is your only criterion, check multiple controlled reviews and inspect full-resolution sample images, paying attention to the focal lengths and apertures you actually use. If you often shoot at slower shutter speeds, the Tamron’s VC may help you get sharper real-world shots by reducing camera shake, even though that isn’t the same as optical sharpness.