First let's look at the rods. As you can see the EVO X rod looks much stronger. Physically it's larger in width and thickness across the beam. The X rods have rod bolts instead of studs, meaning you can upgrade to ARP or other aftermarket bolts easily. The big end is narrower but also larger in diameter than a VIII/IX. The narrower bearing width has less surface area to distribute the load but the larger diameter should help a little. The larger diameter will increase bearing surface speed which can be an issue at very high engine RPM (oil shear issues) but also means the rod journals on the crank are larger and thus stronger.
Stock VIII rod width vs. EVO X rod width
You can see the X rod is almost 3mm wider.
Next with have rod beam thickness
The X rod is about 2mm thicker
Here is shot of the rods side by side
You can see the new X rod has rod bolts rather than studs and nuts like the VIII and IX. This makes upgrading to aftermarket rod bolts very easy.
EVO X - VIII motor comparison details
