From what I gathered in ordering my survival last week, the survival is made of a lighter duck cloth than the workman in order to give the wearer the durability of the workman (or near that) with the comfort of a slightly lighter material. It's dense, tough, and durable. Not as much as canvas, which it is made to resemble (I suppose?), but it's worth the lower quality to have the lightness and breathability, which canvas just doesn't have.

If you're into rough activities, go with the survival. Otherwise, just get a denim or basic.