Is the Tamron 150-600mm f/5-6.3 Di VC USD Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 500mm f/7.1 test image. Observe the contrast and resolution of these results.
Is the Tamron 150-600mm f/5-6.3 Di VC USD Lens set to 500mm f/7.1 sharper than the Sigma 150-500mm f/5-6.3 DG OS HSM Lens set to 400mm f/6.3? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.