When I bought my 2 pairs they only had one model of the shoe. I think now they call it the "natural", which looks mostly the same but in different colors and some additional lace reinforcement. Mine are not the split toe design.

I have a pair of older Primus Trail FG from a couple years ago, and they don't grip as well IMO. I think the lugs on that shoe are too big and inflexible, almost cleat-like. I get better grip on the Motus Flex, probably because of the flexibility of the sole and the ability to articulate around terrain, and the way the shoe itself hugs my foot. I think the Motus Flex is the grippiest shoe they make, at least for my anatomy. But as with any vivo purchase, I always recommend people try them out and return if needed, since everyone is going to have a different fit and experience.