The W430 (grey) has reinforced 'gravel guard' knees, polyester microfiber outer shell and several pockets
http://www.hodgman.com/dyn_prod.php?p=STRW430
The W410 has double layer Taslan lower legs, but not the heavy reinforcement. List price on these is $75 less than the W430.
http://www.hodgman.com/dyn_prod.php?p=STRW410&k=76804