Super Z, 28HP Kohler EFI / 72" XR7, SUSP seat. SZ28KOHEFI72XR7SSA (928036) $11,699
Super Z, 30HP Kohler / 72" XR7, SUSP seat SZ30KOH72XR7SSA (928069) $10,749
The EFI is more expensive due to the components / technology.
The EFI is more fuel efficient and will save you some good money on fuel.
You will find the EFI to be more responsive and more of a on demand type power band, where the carb model has the power it just is not as quick to deliver it.