With Genesis, get the steel caps. Ford used nodular iron on the caps of their performance FEs and later pickup truck FEs, and only used gray iron on non-performance and earlier FEs.
Genesis crossbolted cast caps were cast of gray iron, not nodular. I repeatedly complained to Genesis about this, and got assurances it would be dealt with, but the same huge palleted box of cap castings just kept getting used for production years later. It's possible they've used up that batch and recast a new batch which might be nodular. I wouldn't bank on it, since they didn't seem interested in the nodular issue. You can't tell the Genesis caps are brittle until they crack, since they have the same stiffness and weight as nodular caps. Be careful. They crack just as readily when you torque them into place in the shop as when you are revving a supercharged engine.
Just my opinion,
Shoe.