comparing the soldier 3 to the 4, the only thing i like better on the 4 was the midfoot strap thats functional as opposed to the two stupid straps on the 3.
my two biggest complaints about the soldier 3 were the forefoot zoom was thin and the fit. the 4 kept both of these problems and got rid of the adequate heel zoom cushioning and replaced it with one of the worst implementations of max air ive seen.
the shoe has good traction, but does not use the xdr soles like the soldier 3 did.
the soldier 4 felt higher cut to me and stiffer around the ankle. if you are someone who leans more towards support in the support vs. flexibility you will like these. if you like more flexibility at the ankle, you may not be as fond.
i absolutely loved the 20.5.5s and the soldier 1s, and i thought the soldier 3s were a pretty good shoe. These just didn't do it for me aesthetically, comfort-wise, flexibility-wise, or in any other aspect besides traction and the midfoot strap returning.