Are cast iron or rubber bumper plates better for a home gym?

It depends on what you lift. Across the reviewers we read, cast iron plates are cheaper per pound, take up less room on the bar, and are preferred for slow grinds like squats, deadlifts and presses. Rubber bumper plates are louder-dampening, protect floors, and are essential if you do Olympic lifts or CrossFit-style WODs where the bar may be dropped. Many home-gym threads suggest a hybrid: iron for the bulk of your loading and a pair of bumpers for deadlifts and overhead drops.