Is the Tamron 18-270mm f/3.5-6.3 Di II VC PZD Lens sharp? This page visually answers that question. Shown above are 100% crops from a lab-captured 50mm f/5.0 test image. Observe the contrast and resolution of these results.
Is the Tamron 18-270mm f/3.5-6.3 Di II VC PZD Lens set to 50mm f/5.0 sharper than the Sigma 18-300mm f/3.5-6.3 DC Macro OS HSM C Lens set to 200mm f/16.0? The image quality comparison above also answers that question. Switch between the results to see the sharpness differences between these lenses.