Is the Tamron 150-500mm f/5-6.7 Di III VC VXD Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 300mm f/16.0 test image. Observe the contrast and resolution of these results.
Is the Tamron 150-500mm f/5-6.7 Di III VC VXD Lens set to 300mm f/16.0 sharper than the Sigma 100-400mm f/5-6.3 DG DN OS C Lens set to 400mm f/7.1? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.