Owned all three, I like the grinders the best of the. Pretty much my go pants from mid sept though late oct, when I switch to timberline. I used them for an Alaska caribou hunt the last 10 days or so and they work well.
I feel they are really similar to the mountain pants, seems like the same four way stretch fabric, not overly wind proof but it doesn't RIP though them either. The Mountain pants are slightly heavier and another main difference between them is the leg pocket lay out. The mountain pants with the cargo pockets are more functional, however the flaps are more pronounced. The zip on the grinders pockets are flat. Both will get slight pulls in the fabric over time and heavy use. The mountain pants will have removable knee pads ...i take them out ...I figure I have about 60 days or so the Ginders, and about half that on he mountain pants. Both arent very baggy but are not tight around the boot either, neither are cut like skinny Jean's.
Between these two..if you run colder and cargo pockets are important ...go with the mountain pants. If you run hotter and want more stream line pant ....the grinders.
The Coorugates and Grinders are similar weights, although the fabrics are very different. The CG seem more nylony and also slightly more resistant to pulls, they are also coarser. The pocket lay out is nice, tight to the leg and doesn't catch on anything. I think the grinders are warmer for their weight by far. I also like the cut of the waist/crotch and thighs on the grinders better then the CG, as the CG were tighter in the crotch and thighs the I want for mid season pants.
I feel like the CG are better compared the Sitka Traverse pants.
For mid season I would rank them, Grinders, Mt then CG
For Early season, CG, Grinders, MTP
For later season, MT, Grinders, CG
Hope this helps