Is the Tamron 90mm f/2.8 Di VC USD Macro F017 Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured mm f/ test image. Observe the contrast and resolution of these results.
Is the Tamron 90mm f/2.8 Di VC USD Macro F017 Lens set to mm f/ sharper than the Sigma 105mm f/2.8 DG DN Macro Art Lens set to 105mm f/4.0? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.