Super carriers have a much bigger space budget than submarines, so I wouldn't be surprised if they used less enriched uranium. On the other hand, refueling is

Super carriers have a much bigger space budget than submarines, so I wouldn't be surprised if they used less enriched uranium. On the other hand, refueling is a total pain, so that might put a premium on the total U-235 in the fuel rods (granted, some of the U-238 will breed into plutonium and some of that will burn up, but...).