I think regardless of the pants you wear the knees are going to get worn out and look like chit. Although with using the Carharrt's about 2 mo.s now they've stayed looking pretty good (they fetch $50 a pair though)
When I sold my business the main factor was the uniforms, we wore everything logoed, hats, hoodies, shirts, and even tennis shoes had our logo on them. In winter we wore long sleeve shirts with Lillards silk screen down on the sleeve. We use Cintras service and I paid 100% for the uniforms it was only like $4.95 a week per employee we had 18 employees