For sharpness, nikkor better than tamron for 100 SGD
For colour, nikkor better than tamron for 300 SGD
For contrast, nikkor better than tamron for 100 SGD
For build not including AFS speed, nikkor better than tamron for 150
For AFS (speed), nikkor better than tamron for 50 (cost of speed diff but not moto diff)
so nikkor win picture quality and focusing speed, but tamron win cost effective.
tamron one is much better than kit lens except the color.
for build, kit lens is plastic, tamron is very plastic.
tamron is the best buy for middle zoom lens below 1000 SGD.