The main difference between the models is weight and axle material. They all function the same.

I have older models, as well as current XC2, XC4, XC6, MX4, MX6, and XC12 on various bikes and all of my shoes have the same exact cleats and they all function the same.

All of my bike have been "standardized" on ATAC for about a decade. If it is any help, I have never had a pedal fail, and that includes over 100 cross races and may thousands of rainy gritty commuting miles in the PNW.